DIRECT OBSERVATION OF CHARGE ORDER IN EPITAXIAL FILM OF NdNiO3

ISSN 1423-7369
March 2002
PAUL SCHERRER INSTITUT
LT
Scientific Report 2001
Volume VII
Swiss Light Source
ed. by: Heinz-Josef Weyer, Marlen Bugmann
CH-5232 Villigen PSI
Switzerland
Phone: 0 5 6 / 3 1 0 21 11
Telefax: 0 5 6 / 3 1 0 21 99
http://www.psi.ch/sls
TABLE OF
CONTENTS
INTRODUCTION
A. Wrulich
1
SLS ACCELERATOR
3
ACHIEVEMENTS OF THE SLS COMMISSIONING
4
BEAM DYNAMICS STUDIES ON AN EXTENSION OF SLS FOR GENERATION OF
SUB-PICOSECOND X-RAY PULSES
9
A. Streun, M. Böge, J. Chrin, M. Dach, M. Dehler, C. Gough, W. Joho, T. Korhonen,
S. Leemann, A. Lüdeke, M. Mailand, P. Marchand, M. Muñoz, M. Pedrozzi, L. Rivkin,
W. Portmann, T. Schilcher, V. Schlott, L. Schulz, B. Singh, G. Singh, D. Sütterlin,
A. Wrulich
A. Streun, B. Singh, G. Singh, G. Ingold, V. Schlott
ON THE USE OF CORBA IN HIGH LEVEL BEAM DYNAMICS APPLICATIONS
12
M. Böge, J. Chrin
VACUUM CONDITIONING AND LIFETIME IMPROVEMENT
14
L. Schulz, A. Streun
SLS THIRD HARMONIC SUPERCONDUCTING RF SYSTEM
16
P. Marchand, M. Pedrozzi, A. Anghel (CRPP Lausanne)
BEAM POSITION STABILIZATION
18
M. Böge, T. Schilcher
OPERATION OF THE SLS STORAGE RING RF SYSTEM
20
P. Marchand, M. Pedrozzi, J. Cherix, C. Geiselhart, W. Portmann, W. Tron
RESULTS OF SURVEY AND ALIGNMENT
22
F.Q. Wei, K. Dreyer, H. Umbricht
SLS OPERATION
24
A. Lüdeke
OPERATING EXPERIENCE WITH THE SLS POWER SUPPLIES
25
F. Jenni, M. Horvat, L. Tanner
RESULTS FROM THE HORIZONTAL POSITION MEASUREMENT SYSTEM
28
V. Schlott
STATUS OF THE H LS SYSTEM
30
S. Zelenika
BEAM BASED ALIGNMENT MEASUREMENTS
32
M. Böge
HIGH LEVEL SOFTWARE AND OPERATOR INTERFACE
34
A. Lüdeke, M. Böge, J. Chrin
MEASUREMENT AND COMPENSATION OF LINEAR OPTICAL DISTORTIONS
36
M. Böge, A. Streun
COMMISSIONING RESULTS FOR THE SLS TRANSVERSE MULTIBUNCH
FEEDBACK
37
TOP-UP OPERATION EXPERIENCE
39
M. Dehler, P. Pollet, T. Schilcher, V. Schlott,
R. Bressanutti, D. Bulfone, M. Lonza, L. Zambón (Sincrotrone Trieste)
M. Muñoz
STATUS OF THE SLS CONTROL SYSTEM
41
BEAMLINES, OVERVIEW
43
BEAMLINE AND USERS ASPECTS
44
S. Hunt, M. Dach, M. Grunder, M. Heiniger, C. Higgs, M. Janousch, R. Kappeler,
T. Korhonen, R. Krempaská, J. Krempasky, A. Liideke, D. Maden, T. Pal,
W. Portmann, H. Pruchova, D. Vermeulen
J.F. van der Veen, R. Abela
BEAMLINES, DETAILS
47
SURFACE / INTERFACE SPECTROSCOPY BEAMLINE
48
SURFACE / INTERFACE MICROSCOPY BEAMLINE
50
THE MATERIALS SCIENCE BEAMLINE
52
COMMISSIONING OF THE PROTEIN CRYSTALLOGRAPHY BEAMLINE X06SA
54
LAYOUT OF THE MICROXAS BEAMLINE: DESIGN STUDY
56
L. Patthey, M. Shi, J. Krempasky, T. Schmidt, U. Flechsig, C. Quitmann, R.Betemps,
M. Botkine, R. Abela
C. Quitmann, U. Flechsig, G. Ingold, R. Krempaská, J. Krempasky, F. Nolting,
L. Patthey, T. Schmitt
B.D. Patterson, Th. Bortolamedi, Q. Chen, F. Gozzo, M. Kropf, M. Lange, D. Maden,
B. Schmitt, P.R. Willmott
C. Schulze-Briese, T. Tomizaki, C. Pradervand, R. Schneider, M. Janousch,
W. Portmann, Q. Chen, G. Ingold, D. Rossetti, B. Frauenfelder, C. Zumbach,
P. Hottinger, Ch. Brönnimann, E.F. Eikenberry
D. Grolimund, A.M. Scheidegger, R. Abela, J.F. van der Veen
INSERTION DEVICES: FIRST EXPERIENCES
58
G. Ingold, T. Schmidt
INSERTION DEVICES: CONTROL HARDWARE
64
W. Bulgheroni, T. Korhonen, Ch. Vollenweider, G. Ingold, T. Schmidt
CONCEPTUAL DESIGN: SUB-PICOSECOND HARD X-RAY SOURCE
G. Ingold, A. Streun, B. Singh, R. Abela, P. Beaud, G. Knopp, L. Rivkin, V. Schlott,
Th. Schmidt, H. Sigg, J.F. van der Veen, A. Wrulich, S. Khan (BESSY Berlin)
INSERTION DEVICES: COMPUTER CONTROL
66
T. Korhonen, B. Kalantari, W. Bulgheroni, C. Vollenweider, G. Ingold, T. Schmitt
STATUS OF THE MYTHEN DETECTOR SYSTEM
71
STATUS OF THE PILATUS PROJECT
73
MILLISECOND-SHUTTER FOR EXPOSURE CONTROL
75
B. Schmitt, Ch. Brönnimann, E.F. Eikenberry, M. Naef, F. Gozzo, D. Maden,
B.D. Patterson, R. Horisberger, J. Rothe, S. Streuli, J. Welte
Ch. Brönnimann, E.F. Eikenberry, R. Horisberger, G. Hülsen, M. Näf, B. Schmitt,
S. Streuli
C. Pradervand, D. Rossetti
THE BEAMLINES DATA ACQUISITION AND CONTROL SYSTEM
76
FIRST RESULTS FROM THE X-RAY TOMOGRAPHIC MICROSCOPY STATION
79
J. Krempasky, D. Vermeulen, D. Maden, M. Janousch, R. Krempaská, T. Korhonen,
W. Portmann, M. Grunder, S. Hunt
M. S t a m p a n o n i (PSI/ETHZ), G. Borchert (PSI, IKP Jülich), R. Abela,
B.D Patterson, S. Hunt, D. V e r m e u l e n , P. W y s s ( E M P A ) , P. Rüegsegger (ETHZ)
BRAGG-MAGNIFIER: HIGH PERFORMANCE X-RAY DETECTOR FOR XTM
82
SPIN-RESOLVED FERMI-SURFACE MAPPING ON Ni(111)
85
SCIENTIFIC REPORTS
87
M. Stampanoni (PSI/ETHZ), G. Borchert (PSI, IKP Jülich), R. Abela (PSI),
P. Rüegsegger (ETHZ)
M. Hoesch, M. Muntwiler (PSI/ University of Zurich), V.N. Petrov
(St. Petersburg Techn. University), M. Hengsberger, W. Auwärter, T. Greber,
J. Osterwalder (University of Zurich)
DIRECT OBSERVATION OF CHARGE ORDER IN EPITAXIAL FILM OF NdNi0
88
STRUCTURAL DISORDER BELOW THE M ETAL-INSULATOR TRANSITION
IN Ca Ru0
89
PROPAGATION OF A FOCUSED X-RAY BEAM WITHIN A PLANAR
X-RAY WAVEGUIDE
90
DYNAMICS OF CONFINED COLLOIDS
92
TIME-RESOLVED EXAFS WITH SINGLE X-RAY PULSES AT 1 KHZ
94
UNCOMPENSATED SPINS IN ANTIFERROMAGNETIC NIO COUPLED
TO A FERROMAGNET
97
PEEM MEASUREMENT OF MICROSTRUCTURED NIO THIN FILMS
98
3
U. Staub, G.I. Meijer (IBM-Rueschlikon), F. Fauth (ESRF),
R. Allenspach (IBM-Rueschlikon), J.G. Bednorz, J. Karpinski, S.M. Kazakov (ETHZ),
L. Paolasini, F. d'Acapito (ESRF)
2
4
U. Staub, B. Schmitt, F. Gozzo, T. Bortolamedi, K. Conder,
C. Hörmann (University of Erlangen), P. Pattison (University of Lausanne),
D. Sheptyakov
J.H.H. Bongaerts, G.H. Wegdam (University of Amsterdam), M. Drakopoulos (ESRF),
C. David, H. Keymeulen, T. Lackner, J.F. van der Veen (PSI/ETHZ)
J.H.H. Bongaerts, J. Miguel (University of Amsterdam)
U. Flechsig, J.F. van der Veen (PSI/ETHZ)
C. Bressler, M. Chergui, F. Van Mourik (University of Lausanne),
M. Saes (PSI/University of Lausanne),
R. Abela, D. Grolimund (PSI),
R.W. Falcone, S.L. Johnson, A.M. Lindenberg (UC Berkeley),
P.A. Heimann, R.W. Schoenlein (ALS)
F. Nolting, H. Ohldag (LBNL/SSRL), E. Arenholz (LBNL), A. Scholl (LBNL),
A T . Young (LBNL), J. Stöhr (SSRL)
F. Nolting, L. Heydermann, P.R. Willmott
HIGH RESOLUTION TESTS OF THE SLS POWDER DIFFRACTOMETER
F. Gozzo, Th. Bortolamedi, M. Lange, D. Maden, J. Rothe, B. Schmitt, J. Welte,
B.D. Patterson
99
RESIDUAL STRESS ANALYSIS IN CUBIC LPPS ZIRCONIA COATINGS USING
SYNCHROTRON RADIATION X-RAY DIFFRACTION (XRD)
102
NOVEL MATERIALS GROWN WITH PULSED LASER ABLATION EPITAXY
104
Th. Bortolamedi, M. Lange, D. Maden, B. Schmitt, B.D. Patterson, F. Gozzo, M. Loch,
G. Barbezat (Sulzer Metco Wohlen)
P.R. Willmott, B.D. Patterson, D. Rossetti
APPENDIX
106
1
INTRODUCTION
A.
OVERVIEW
Y e a r 2 0 0 1 s a w t h e t r a n s f e r of t h e S L S f r o m c o n s t r u c tion to c o m m i s s i o n i n g a n d o p e r a t i o n . After h a v i n g
s t o r e d t h e first b e a m a l r e a d y in D e c e m b e r 2 0 0 0 , f r o m
J a n u a r y 2 0 0 1 o n the c o m m i s s i o n i n g of t h e full a c c e l erator c o m p l e x w a s restarted a n d c o n t i n u e d up t o J u l y
2 0 0 1 , so that f r o m A u g u s t 1 o n , 7 0 % of t h e r u n n i n g
t i m e c o u l d be d e d i c a t e d t o u s e r o p e r a t i o n .
s t
O n O c t o b e r 1 9 , the S L S w a s officially o p e n e d . A n
e x t r a o r d i n a r y c e r e m o n y t o o k place, w h e r e several
h u n d r e d g u e s t s w e r e t r e a t e d t o a m i x t u r e of optical,
a c o u s t i c a l a n d culinary delights.
th
HIGHLIGHTS
M a j o r highlights in 2 0 0 1 w e r e the full c o m m i s s i o n i n g
of the a c c e l e r a t o r s y s t e m s , t h e a c h i e v e m e n t of all
specified p a r a m e t e r s of the s t o r a g e ring a n d further
o p t i m i s a t i o n of Linac u n d B o o s t e r in o r d e r to g u a r a n tee a reliable o p e r a t i o n of t h e injection c h a i n .
F u r t h e r m o r e , o p e r a t i o n of t h e four initial b e a m l i n e s
w a s started. I m p o r t a n t p r o g r e s s w a s m a d e in the o p timization of t h e protein c r y s t a l l o g r a p h y a n d material
s c i e n c e b e a m l i n e s , allowing t h e a c c e s s of e x p e r t users d u r i n g the s e c o n d half of year 2 0 0 1 .
Storage Ring Commissioning
All global m a c h i n e p a r a m e t e r s , as e n e r g y , c u r r e n t a n d
emittance have been achieved according to specifications.
B e a m p e r f o r m a n c e p a r a m e t e r s , a s c l o s e d orbit d e v i a tion, beta beat, s p u r i o u s d i s p e r s i o n a n d e m i t t a n c e
c o u p l i n g w e r e o p t i m i z e d a n d a n excellent p e r f o r m a n c e
characteristics c o u l d be r e a c h e d with n e w d e v e l o p e d
c o r r e c t i o n a l g o r i t h m s . A s l o w orbit f e e d b a c k s y s t e m
w a s set in o p e r a t i o n , w h i c h is d y n a m i c a l l y c o r r e c t i n g
the global orbit, t h u s stabilizing the s o u r c e point positions of insertion d e v i c e s a s well as b e n d i n g m a g n e t s .
Short a n d long t e r m stabilities of < 1 urn at t h e locations of t h e insertion d e v i c e s a n d a n e n e r g y stability of
2 10" w e r e a c h i e v e d .
5
A prototype m u l t i - b u n c h f e e d b a c k s y s t e m w a s t e s t e d
a n d r e v e a l e d p r o m i s i n g behaviour. Further t e s t s a n d
the full s y s t e m integration are b e i n g p e r f o r m e d .
Critical o p e r a t i o n m o d e s of t h e s t o r a g e ring w e r e installed a n d g o o d p e r f o r m a n c e w a s r e a c h e d . T o p - u p
injection b e c a m e t h e favourite o p e r a t i o n m o d e of t h e
u s e r s , d u e t o its e x t r e m e l y beneficial effect o n b e a m
stability by c o n s t a n t t h e r m a l load on b e a m l i n e optics
and machine equipment.
For t h e l o w - g a p o p e r a t i o n m o d e c o u l d be verified, that
the lifetime r e d u c t i o n d u e t o elastic b e a m - g a s scattering c a n be h a n d l e d d o w n t o 4 m m g a p a n d the injection efficiency c a n be m a i n t a i n e d at this low g a p for a
Wrulich
m i n i m i z e d c o u p l i n g of t h e b e t a t r o n m o t i o n
horizontal a n d vertical plane.
between
T h e n e w d e v e l o p m e n t s , w h i c h w e r e p e r f o r m e d to
r e a c h high position stability, as the digital p o w e r s u p ply controller a n d t h e f o u r - c h a n n e l B P M e l e c t r o n i c s ,
r e v e a l e d v e r y satisfactory p e r f o r m a n c e . In c o m b i n a tion with t o p up, t h e s e n e w d e v e l o p m e n t s are the
g u a r a n t e e for the e x c e p t i o n a l l o n g - t e r m position s t a bility.
T h e d e s i g n v a l u e s for t h e v a c u u m p r e s s u r e a n d the
b e a m lifetime c o u l d be a c h i e v e d after o n l y 6 m o n t h s of
o p e r a t i o n . T h e g o o d results d e m o n s t r a t e that t h e c o n c e p t of stainless steel a n t e c h a m b e r with integrated
c o p p e r a b s o r b e r s a n d t h e external b a k e out w a s s u c cessful.
Beamlines
T h e four b e a m l i n e s of the initial p h a s e are b a s e d o n
insertion d e v i c e s , w h i c h w e r e installed in 2 0 0 1 , b e g i n ning with t h e m i n i - g a p w i g g l e r for the material s c i e n c e
b e a m l i n e in April. All of t h e m are high p e r f o r m a n c e
d e v i c e s , c o n s i s t i n g b e s i d e s the w i g g l e r of a n in v a c u u m mini u n d u l a t o r a n d t w o twin helical d e v i c e s .
T h e transition f r o m c o m m i s s i o n i n g t o user o p e r a t i o n
started a l r e a d y in M a y 2 0 0 1 with the first o p e r a t i o n of
t h e protein c r y s t a l l o g r a p h y line.
For t h e protein c r y s t a l l o g r a p h y b e a m l i n e , t h e novel
c o n c e p t of p r o d u c i n g hard X - r a y s f r o m the higher
h a r m o n i c s of an in v a c u u m insertion d e v i c e c o u l d be
s u c c e s s f u l l y set in o p e r a t i o n . First b e a m f r o m the U 2 4
u n d u l a t o r w a s available in M a y 2 0 0 1 . T h e u n d u l a t o r
s p e c t r u m , m e a s u r e d at 10 m m g a p , s h o w e d g o o d
a g r e e m e n t with theory. It c o u l d be d e m o n s t r a t e d that
t o p up o p e r a t i o n h a s no d e t r i m e n t a l effect o n the data
quality e v e n w i t h o u t gating t h e data collection. S e v e r a l
M A D a n d S A D e x p e r i m e n t s w e r e carried out. Expert
u s e r g r o u p s a l r e a d y s o l v e d a n u m b e r of structures.
T h e wiggler of t h e material s c i e n c e b e a m l i n e ( M S )
w a s installed in J u l y 2 0 0 1 . A l r e a d y before that, first
light w a s t a k e n f r o m the b e n d i n g m a g n e t in M a y in
o r d e r t o c h e c k t h e a l i g n m e n t of the optical c o m p o n e n t s . O n l y after installation of a rotating h i g h - p o w e r
c a r b o n filter, t h e insertion d e v i c e c o u l d be c l o s e d to
t h e m i n i m u m g a p a n d it w a s possible to e x p e r i m e n tally d e t e r m i n e t h e w i g g l e r s p e c t r u m o v e r the full
r a n g e . In N o v e m b e r a n d D e c e m b e r 2 0 0 1 e x p e r t u s e r s
w e r e starting with e x p e r i m e n t s : t h e X T M c o l l a b o r a t i o n ,
9 p o w d e r diffraction u s e r s , 2 r e f l e c t o m e t r y u s e r s a n d 1
s p e c t r o s c o p y user.
For the S u r f a c e a n d interface s p e c t r o s c o p y b e a m l i n e
(SIS), t h e twin u n d u l a t o r U E 2 1 2 a n d t h e optics of the
b e a m l i n e are o p e r a t i o n a l a n d provide light with high
resolution a n d high spectral purity. T h e e x p e r i m e n t a l
station with t h e h i g h - r e s o l u t i o n p h o t o e l e c t r o n s p e c t r o m e t e r w a s installed in spring 2 0 0 1 . T h e
2
c o m m i s s i o n i n g of the b e a m l i n e started in A u g u s t
2 0 0 1 , w h e n the first s p e c t r u m w a s m e a s u r e d by an
energy
scan
of
the
monochromator.
The
e l e c t r o m a g n e t i c twin u n d u l a t o r w a s installed in J u n e
a n d in O c t o b e r the q u a s i p e r i o d i c m o d e c o u l d be
t e s t e d , resulting in a p h o t o n b e a m with high spectral
purity
of
less
than
0.5%
higher
harmonic
contamination.
T h e m a j o r c o m p o n e n t s of the s u r f a c e a n d interface
m i c r o s c o p y b e a m l i n e ( S I M ) w e r e installed a n d c o m m i s s i o n i n g w a s s t a r t e d . T h e m i c r o s c o p e w a s delivered
in M a r c h 2 0 0 1 a n d within 3 d a y s first i m a g e s c o u l d be
t a k e n . T h e first e l e m e n t of t h e U E 5 6 p e r m a n e n t m a g net twin u n d u l a t o r w a s c o m p l e t e d in O c t o b e r . P h a s e
errors b e l o w 3 d e g r e e s allow w o r k at higher h a r m o n ics with m o d e s t loss in intensity. A first flux c u r v e w a s
m e a s u r e d in D e c e m b e r .
NEW DEVELOPMENTS AND UPGRADING
A s part of an u p g r a d e p r o g r a m , t h r e e central m a g n e t s
of the triplet b e n d a c h r o m a t structure of the s t o r a g e
ring will be r e p l a c e d by s u p e r b e n d s . T h e y are a c o m bination of e l e c t r o m a g n e t a n d p e r m a n e n t m a g n e t s
with a field e n h a n c e m e n t in the central region f r o m 1.4
to 3.1 T e s l a a n d a c o r r e s p o n d i n g shift of t h e critical
energy. In this w a y , a flux i n c r e a s e of m o r e t h a n o n e
o r d e r of m a g n i t u d e is a c h i e v e d for h i g h e r p h o t o n e n ergies.
T h e d e v e l o p m e n t of the s u p e r c o n d u c t i n g higher harm o n i c cavity w a s p r o g r e s s i n g a c c o r d i n g t o s c h e d u l e .
Fabrication a n d cold t e s t s of the cavity w e r e c o m pleted, revealing satisfactory behaviour. By l e n g t h e n ing the b u n c h a n d t h e r e f o r e r e d u c i n g t h e c h a r g e c o n c e n t r a t i o n , this s y s t e m will further i m p r o v e the b e a m
lifetime, w h i c h is d o m i n a t e d by T o u s c h e k s c a t t e r i n g .
T h e F E M T O project is targeting t h e g e n e r a t i o n of s u b p i c o s e c o n d optical p u l s e s by b e a m slicing. It c o n s i s t s
of a m o d u l a t o r w i g g l e r for laser b e a m slicing a n d a
radiator undulator - of t h e u X A S b e a m l i n e - for t h e
e m i s s i o n . Both of t h e m will be i m p l e m e n t e d in o n e of
the extra long straight s e c t i o n s (11 m ) of t h e S L S ,
m i n i m i z i n g in this w a y the b e a m deterioration b e t w e e n
m o d u l a t o r a n d radiator.
P r o g r e s s w a s m a d e in c o n c e p t u a l i s i n g the X - r a y a b sorption spectroscopy
beamline. Several
optical
s c h e m e s , o p t i m i z e d for m i c r o f o c u s s i n g , w e r e e v a l u a t e d with r e s p e c t to spatial resolution, p h o t o n flux a n d
e n e r g y resolution. A m i n i - g a p i n - v a c u u m u n d u l a t o r will
s e r v e as radiation s o u r c e .
OUTLOOK
In year 2 0 0 2 , the total n u m b e r of shifts per m o n t h will
i n c r e a s e steadily. For t h e first half year, a n a v e r a g e of
5 9 shifts per m o n t h is e n v i s a g e d , w h e r e f r o m a b o u t
8 0 % will be d e d i c a t e d to user o p e r a t i o n .
3
SLS ACCELERATOR
4
ACHIEVEMENTS OF THE SLS COMMISSIONING
A. Streun,
A. Lüdeke,
M. Böge, J. Chrin, M. Dach, M. Dehler, C. Gough, W. Joho, T. Korhonen, S. Leemann,
M. Mailand, R Marchand, M. Muñoz, M. Pedrozzi, L. Rivkin, W. Portmann,
T. Schilcher,
V. Schlott, L Schulz, B. Singh, G. Singh, D. Sütterlin, A. Wrulich
Commissioning
of the storage ring started in December 2000, the most important performance
figures were
achieved until dune 2001. The four initial beamlines came into operation between duly and November.
Since
August 1 , 2001 SLS operates to 70 % for users.
We will summarize
the achievements
on storage ring performance
and agreement
with the design
calculations concerning
lattice calibration,
stored beam current and lifetime. Further improvements
on linac and
booster, already commissioned
in 2000, will be mentioned.
st
TIME SCHEDULE
C o m m i s s i o n i n g of t h e S L S 100 M e V linac [21] a n d
t h e 2.4 G e V b o o s t e r s y n c h r o t r o n [15] to d e s i g n perform a n c e w a s d o n e b e t w e e n M a r c h a n d April, resp. f r o m
July to S e p t e m b e r 2 0 0 0 . First s t o r e d b e a m in t h e ring
w a s o b t a i n e d by Dec. 15, 2 0 0 0 [22].
M a i n c o m m i s s i o n i n g of t h e s t o r a g e ring w a s d o n e
f r o m J a n u a r y to July 2 0 0 1 , s o that the m a c h i n e c o u l d
start to run 7 0 % for u s e r s f r o m A u g u s t 1 , 2 0 0 1 , a s
scheduled.
Betaferons
X/dP [m]
[m]
• 1 0
4
« 0. 1
1
1
4
t h e i n - v a c u u m u n d u l a t o r U 2 4 (on loan f r o m Spring-8)
for protein c r y s t a l l o g r a p h y ( P X ) , t h e e l e c t r o m a g n e t i c
twin u n d u l a t o r U E 2 1 2 for surface a n d interface s p e c t r o s c o p y (SIS) a n d t h e A p p l e t y p e twin undulator U E 5 6
for surface a n d interface m i c r o s c o p y ( S I M ) .
Table 1 : S L S s t o r a g e ring p a r a m e t e r s
Energy
2.4
GeV
m
Circumference
288
RF frequency
500
MHz
Tunes
Natural c h r o m a t i c i t i e s
Momentum compaction
Radiation loss per t u r n
Damping times
Emittance
Relative e n e r g y s p r e a d
B u n c h length
20.41 / 8 . 1 9
-66 / -21
6.510"
4
512
keV
9.0/9.0/4.5
5.0
8.610"
4
ms
nmrad
4
mm
COMMISSIONING MILESTONES
F i g . 1 : S L S s t o r a g e ring optics: o n e sixth of the ring
(i.e. 9 6 m or 2 arcs) is s h o w n . (ß , r] solid, ß dotted)
x
y
F e b . 2 8 100 m A of s t o r e d b e a m c u r r e n t r e a c h e d , operation in all lattice optics: relaxed, s t a n d a r d low
e m i t t a n c e a n d distributed d i s p e r s i o n
THE SLS STORAGE RING
Apr. 8
T h e S L S s t o r a g e ring is a 12 T B A (triple-bend a c h r o mat) ( 8 7 l 4 ° / 8 ° ) lattice with six s h o r t straights of 4 m
length, t h r e e m e d i u m o n e s of 7 m a n d t h r e e long o n e s
of 11 m. Four cavities of 6 5 0 kV p e a k voltage occ u p y t w o s h o r t straights, injection o c c u p i e s o n e long
straight. T h e lattice is d e s i g n e d to provide an emitt a n c e of 5 n m r a d at 2.4 G e V with d i s p e r s i o n free
straights a n d « 4 n m r a d w h e n a l l o w i n g s o m e dispers i o n . 174 q u a d r u p o l e s with i n d e p e n d e n t p o w e r s u p plies g r o u p e d into 2 2 soft families allow for a large flexibility, 120 s e x t u p o l e s in 9 families are carefully bala n c e d to provide large d y n a m i c a p e r t u r e s . E a c h 7 2
horizontal a n d vertical c o r r e c t o r s a n d 7 2 B P M s control
t h e orbit, 6 s k e w q u a d r u p o l e s in 3 families s u p p r e s s
c o u p l i n g . Figure 1 a n d table 1 s h o w lattice f u n c t i o n s
a n d list basic p a r a m e t e r s of t h e o p t i c s presently u s e d .
A p r . 2 6 M e a s u r e m e n t a n d c o r r e c t i o n of b e t a f u n c t i o n s
A n initial set of four insertion d e v i c e s c o n s i s t s of
t h e high field w i g g l e r W 6 1 for m a t e r i a l s s c i e n c e ( M S ) ,
First single b u n c h o p e r a t i o n
May 4
Orbit c o r r e c t i o n d o w n t o m i c r o n levels
Jun. 5
D e s i g n c u r r e n t of 4 0 0 m A r e a c h e d
J u n . 2 3 First t o p up injection
J u l . 10
PX b e a m l i n e operational
J u l . 19
1 Hz orbit f e e d b a c k operational
Aug. 9
First o p e r a t i o n of m u l t i b u n c h f e e d b a c k s y s t e m
Aug. 9
M S b e a m l i n e operational
A u g . 10 SIS beamline operational
N o v . 2 1 S I M b e a m l i n e operational
5
LATTICE CALIBRATION
Circumference
Several c i r c u m f e r e n c e m e a s u r e m e n t s b a s e d on orbit
c o r r e c t i o n or s e x t u p o l e c e n t e r i n g by variation of R F freq u e n c y c o n f i r m e d t h e d e s i g n v a l u e within 0.5 m m .
2 0 5 r e s o n a n c e limiting t h e e n e r g y a c c e p t a n c e a n d with
it t h e lifetime [35].
Fc =
4.9965413e+08 Hz
0.40 r
Emittances and energy spread
I m a g i n g of t h e X - r a y part of t h e s y n c h r o t r o n radiation by
m e a n s of a p i n h o l e c a m e r a c o n f i r m e d t h e d e s i g n v a l u e
of t h e horizontal e m i t t a n c e .
T h e vertical e m i t t a n c e is c r e a t e d parasitically by lattice imperfections. S i m u l a t i o n s p r e d i c t e d a m o s t likely
v a l u e n e a r 15 p m r a d [3]. M e a s u r e m e n t s with t h e pinhole c a m e r a g a v e larger v a l u e s a r o u n d 7 5 p m - r a d .
F r o m difference orbit m e a s u r e m e n t s of r m s vertical disp e r s i o n a n d T o u s c h e k lifetime m e a s u r e m e n t s [35] valu e s of 2 0 to 3 0 p m r a d w e r e d e r i v e d .
P r e c i s e m e a s u r e m e n t s of t h e e n e r g y s p r e a d c o u l d
not yet b e d o n e . H o w e v e r b o t h pinhole c a m e r a i m ages and photon spectra taken from the U24 undulator
[28] indicate, that t h e effective e n e r g y s p r e a d c o u l d b e
larger t h a n t h e d e s i g n v a l u e by 5 0 to 1 0 0 % ( d e p e n d i n g
on the operation mode).
Working point
For m o s t of t h e y e a r 2 0 0 1 a w o r k i n g point ( h o r i z o n tal/vertical tune) at 2 0 . 3 8 / 8 . 1 6 , deviating f r o m t h e d e s i g n 2 0 . 8 2 / 8 . 2 8 but providing a l m o s t e q u a l e m i t t a n c e ,
w a s u s e d . R e c e n t l y a n even better point w a s f o u n d at
2 0 . 4 1 / 8 . 1 9 . H i g h e s t injection efficiency a n d b e a m lifet i m e a r e t h e criteria for o p t i m i z a t i o n .
T h e t u n i n g r a n g e is quite large: In t h e horizontal t h e
integer 2 0 c a n b e a p p r o a c h e d to 0.05, t h e half integer
2 0 . 5 to 0.005. T h e n o n - s y s t e m a t i c third integer 2 0 | h a s
to b e c r o s s e d quickly in o r d e r to k e e p t h e b e a m .
In t h e vertical t h e integer 8 c a n b e a p p r o a c h e d by
0 . 0 1 . T h e b e a m is not lost o n t h e half integer 8.5 but
s h o w s s o m e s t o c h a s t i c m o t i o n indicating a rather narrow r e s o n a n c e a n d stabilization d u e to d e t u n i n g .
A n alternative w o r k i n g point to r e d u c e t h e vertical
b e a m s i z e w a s f o u n d at 2 0 . 3 8 / 1 1 . 1 6 . T h e p e r f o r m a n c e
in t e r m s of injection efficiency a n d e m i t t a n c e is similar to t h e s t a n d a r d w o r k i n g point at 2 0 . 3 8 / 8 . 1 6 , but for
large s t o r e d b e a m current, a n horizontal instability w a s
o b s e r v e d , w h i c h c o u l d not b e s u p p r e s s e d by i n c r e a s e d
c h r o m a t i c i t y [31]. T h i s p h e n o m e n o n r e q u i r e s further investigation.
Chromaticities
T h e c h r o m a t i c i t i e s w e r e m o v e d by d e s i g n f r o m t h e natural -66/-21 to + 1 / + 1 a n d f o u n d to b e + 1 . 6 / + 0 . 5 with t h e
theoretical s e x t u p o l e settings. H o w e v e r b e a m stability at large c u r r e n t s requires i n c r e a s e to a p p r o x . + 5 / + 5
(see b e l o w ) . T h e variation of t u n e with m o m e n t u m deviation s h o w s excellent a g r e e m e n t with t h e o r y a s s h o w n
in f i g u r e 2. T h e s t r o n g n e g a t i v e horizontal s e c o n d order c h r o m a t i c i t y m a k e s t h e n o n - s y s t e m a t i c third integer
n mh
I
-6
-4
0
-2
dp/p
1
2
4
[%]
F i g . 2:
Fractional t u n e s a s a f u n c t i o n of relative m o m e n t u m d e v i a t i o n .
A f r e q u e n c y variation of
+ 1 0 / - 1 2 k H z t r a n s l a t e s to a m o m e n t u m deviation of
- 4 . 7 / + 3 . 0 % d u e to t h e large nonlinear m o m e n t u m
c o m p a c t i o n : a = 6.5 • 1 0 ~ , ai = 4.6 • 1 0 ~ . T h e solid
lines s h o w t h e T R A C Y [1] s i m u l a t i o n , t h e d i a m o n d s a r e
m e a s u r e m e n t s , u p p e r c u r v e is horizontal.
4
3
a
Betafunctions
S i n c e all 1 7 4 q u a d r u p l e s at S L S a r e e q u i p p e d with individual p o w e r s u p p l i e s , it w a s straightforward to m e a s u r e t h e b e t a f u n c t i o n s at e a c h q u a d r u p o l e f r o m t u n e
variation. Individual q u a d r u p o l e gradient e r r o r s w e r e
fitted to t h e m e a s u r e m e n t s . T h e inverse of t h e s e e r r o r s
w a s a d d e d to t h e g r a d i e n t s a n d t h e b e t a f u n c t i o n s w e r e
m e a s u r e d a g a i n . Eventually, t h e r m s deviation of m e a s u r e d to d e s i g n b e t a f u n c t i o n s a c h i e v e d w a s only 4 % in
t h e horizontal a n d 3 % in t h e vertical [5].
BEAM CURRENT
W h e n increasing the stored beam current towards the
d e s i g n v a l u e of 4 0 0 m A , t h r e e p r o b l e m s h a d to b e overcome:
Higher order cavity modes
Higher o r d e r m o d e s ( H O M s ) in t h e four cavities, leading
to s u d d e n b e a m loss b e y o n d s o m e t h r e s h o l d current,
h a d to b e d e t u n e d by m e a n s of cavity t e m p e r a t u r e v a r i ation a n d t h e H O M f r e q u e n c y shifters in o r d e r not to
c o i n c i d e with t h e b e a m s p e c t r u m [17].
Presently, b e a m c u r r e n t s u p to 3 0 0 m A a r e routinely
s t o r e d , w h e r e a s r e p r o d u c t i o n of t h e 4 0 0 m A requires
s o m e d e d i c a t e d effort o n H O M s u p p r e s s i o n .
Multibunch instability
Above s o m e threshold current depending on the
o p e r a t i n g c o n d i t i o n s , a p p e a r s a vertical instability. T h i s
l e a d s to s h a k i n g of t h e b e a m a n d s u b s e q u e n t l o s s e s
of large s e c t i o n s f r o m t h e s t o r e d b u n c h train.
6
T h e instability is still u n d e r investigation. It s h o w s
s i g n a t u r e s of both ion t r a p p i n g a n d resisitive wall
impedance.
Indications for ion t r a p p i n g :
• T h e t h r e s h o l d c u r r e n t for o n s e t of t h e oscillations
i n c r e a s e s with i m p r o v e d v a c u u m conditions.
• T h e t h r e s h o l d c u r r e n t i n c r e a s e s with t h e length of
a g a p in t h e b u n c h train, b e c a u s e ions t r a p p e d
in t h e electrostatic potential of t h e b e a m c a n b e
d e s t a b i l i z e d by t h e gap.
• Appearently, l o s s e s o c c u r mainly f r o m t h e b u n c h
train's tail r e g i o n , w h e r e t h e s h a k i n g of t h e b e a m
is e x p e c t e d t o h a v e largest a m p l i t u d e s .
Indications for resistive wall i m p e d a n c e :
• T h e negative b e t a t r o n s i d e b a n d s of t h e revolution h a r m o n i c s in t h e b e a m s p e c t r u m a r e s t r o n g e r
t h a n t h e positive s i d e b a n d s , w h i c h is typical for
a n interaction with t h e resistivity of t h e v a c u u m
chamber.
• T h u s , t h e t h r e s h o l d c u r r e n t is larger if t h e vertical
t u n e is b e l o w a n integer t h a n a b o v e .
• T h e situation a g g r a v a t e d after installation of t h e
10 m long stainless steel v a c u u m c h a m b e r for t h e
SIS-undulator.
• M A F I A - s i m u l a t i o n s p r e d i c t e d only 3 u n s t a b l e
m o d e s without, but 2 0 with t h e n a r r o w v a c u u m
c h a m b e r s installed.
T h e r e a r e t w o w a y s t o s u p p r e s s t h e instability:
• I n c r e a s e of horizontal a n d vertical c h r o m a t i c i t i e s
t o large positive v a l u e s a s + 5 . However, t h e req u i r e d i n c r e a s e of s e x t u p o l e s t r e n g t h l e a d s to a
deterioration of t h e d y n a m i c a p e r t u r e a n d with it
t o reduction of injection efficiency.
• O p e r a t i o n of t h e t r a n s v e r s e m u l t i b u n c h f e e d b a c k
s y s t e m ( T M B F ) [9]: In fact, first o p e r a t i o n of t h e
T M B F p r o v i d e d a r e d u c t i o n of t h e c h r o m a t i c i t y req u i r e d t o s u p p r e s s t h e instability. C o m m i s s i o n i n g
of t h e s y s t e m is in p r o g r e s s [10].
LIFETIME
D e p e n d i n g on t h e o p e r a t i o n m o d e , b e a m lifetime is
d o m i n a t e d either by elastic s c a t t e r i n g o n residual g a s
nuclei or by T o u s c h e k effect, i.e. s c a t t e r i n g of e l e c t r o n s
within t h e b u n c h . A n o t h e r non-negligible contribution is
b r e m s s t r a h l u n g on residual g a s nuclei.
M e a s u r e m e n t s of lifetime w h i l e m o v i n g a s c r a p e r
into t h e b e a m isolated t h e elastic s c a t t e r i n g c o n t r i b u tion. Variations of R F voltage, t u n e a n d single b u n c h
c u r r e n t w e r e d o n e t o investigate t h e T o u s c h e k lifetime.
T h e measurements show a very good agreement
with theory. T o u s c h e k lifetime t u r n e d out to b e limited
by an e n e r g y a c c e p t a n c e restriction d u e to t h e proximity of t h e 2 0 | r e s o n a n c e (see a b o v e ) . T h e d é p e n d a n c e o n R F v o l t a g e p r o v i d e d a n e s t i m a t e for t h e vertical e m i t t a n c e of a p p r o x . 3 0 p m r a d [35], [27].
Presently, a b e a m lifetime of a p p r o x . 10 h o u r s is
a c h i e v e d with 2 0 0 m A of b e a m c u r r e n t distributed o n
3 9 0 of 4 8 0 available buckets.
BEAM STABILITY
T h e c l o s u r e of t h e four kicker injection b u m p [11 ] h a s
b e e n o p t i m i z e d , leaving a b e t a t r o n oscillation of t h e
s t o r e d b e a m , w h i c h a m o u n t s to only 150 ¿¿m h o r i z o n tally ( r m s f r o m all B P M s for next t u r n s following injection).
T h e jitter of t h e s t o r e d b e a m d u e to t h e b o o s t e r ' s
3 Hz r a m p i n g c y c l e w a s m e a s u r e d t o b e ss 0.3 ¿¿m at
t h e location of t h e insertion d e v i c e s . P h a s e oscillations
of t h e R F a r e well b e l o w 1° over t h e w h o l e f r e q u e n c y
r a n g e u p to 1 0 0 k H z . T h e a m p l i t u d e s f r o m 5 0 Hz a n d
h a r m o n i c v i b r a t i o n s in d i s p e r s i v e regions a r e of t h e order of 1 m i c r o n .
A 1 Hz orbit f e e d b a c k [2] h a s b e e n installed t o s t a bilize position a n d a n g l e of t h e b e a m in t h e insertion
d e v i c e s at levels of 0.6 ¿¿m a n d 0.3 ¿¿rad over a p e r i o d
of an e x p e r i m e n t a l shift [4].
T h e b e a m intensity is kept c o n s t a n t at t h e 0.1 %
level by m e a n s of t o p - u p injection every few s e c o n d s
[19].
INSERTION DEVICES
Installation d a t e s of t h e insertion d e v i c e s for t h e four
initial b e a m l i n e s [12]
• April
Thermal problems
10, 2 0 0 1 :
in v a c u u m u n d u l a t o r
U24
in
straight 6 S .
D u e t o a m i s s t e e r i n g of t h e b e a m orbit, b e n d i n g m a g net radiation m i s s i n g t h e a b s o r b e r s c a n lead to local
o v e r h e a t i n g of t h e v a c u u m c h a m b e r , w h i c h o n c e even
c a u s e d a leak. After installation of several t e m p e r a t u r e
s e n s o r s all over t h e v a c u u m c h a m b e r , an orbit w a s taylored by introducing d e d i c a t e d b u m p s for m i n i m i z a t i o n
of v a c u u m c h a m b e r h e a t i n g .
• July 2 5 , 2 0 0 1 : first m o d u l e of t h e e l e c t r o m a g n e t i c
elliptic twin u n d u l a t o r U E 2 1 2 in straight 9L.
D u e t o t h e s t r o n g e r vertical f o c u s i n g , t h e alternative
o p t i c s with t h e w o r k i n g point at 2 0 . 3 8 / 1 1 . 1 6 c o u l d o p e r a t e w i t h o u t t h e s e orbit b u m p s [31].
• Nov. 12, 2 0 0 1 : first m o d u l e of t h e S a s a k i t y p e
elliptic twin u n d u l a t o r U E 5 6 in straight 11L.
• July 3 0 , 2 0 0 1 : w i g g l e r W 6 1 in straight 4 S with
v a c u u m c h a m b e r of inner height 12 m m .
• Oct. 15, 2 0 0 1 : s e c o n d m o d u l e of U E 2 1 2 .
• J a n . 7, 2 0 0 2 : r e d u c t i o n of W 6 1 c h a m b e r to 8 m m .
7
• July 2 0 0 2 :
stalled.
s e c o n d m o d u l e of U E 5 6 to b e in-
S t u d i e s on h o w c l o s i n g a n d o p e n i n g t h e insertion d e v i c e s affects t h e s t o r e d b e a m h a v e b e e n s t a r t e d a n d
i m p l e m e n t a t i o n of f e e d f o r w a r d t a b l e s is in p r o g r e s s .
T h i s c o n c e r n s calculation of local c o r r e c t i o n s of t h e
insertion d e v i c e s ' orbit distortion f r o m orbit r e s p o n s e
m e a s u r e m e n t s a n d t u n e shift c o m p e n s a t i o n s . U p to
n o w all insertion d e v i c e s w e r e f o u n d to h a v e little i m pact o n t h e orbit a n d t o c a u s e rather small t u n e shifts
in a g r e e m e n t with t h e p r e d i c t i o n s [30], [29].
LINAC IMPROVEMENTS
In t h e b e g i n n i n g , t h e linac w a s o p e r a t i n g in m u l t i - b u n c h
m o d e , providing a train of b u n c h e s of low c h a r g e . In
o r d e r t o c r e a t e s h a r p g a p s in t h e b e a m s t o r e d in t h e
ring, t h e alternative m o d e t o p r o v i d e highly c h a r g e d
single b u n c h e s [21] h a s b e e n o p t i m i z e d further a n d
m e a n w h i l e is u s e d routinely. A t r a n s m i s s i o n efficiency
of 9 0 % t h r o u g h t h e linac h a s b e e n a c h i e v e d . After
± 1 % e n e r g y filtering 6 5 % r e m a i n for injection into t h e
booster.
Infrared c o h e r e n t transition radiation h a s b e e n c o u pled out, c o h e r e n c e w a s p r o v e n by o b s e r v a t i o n of t h e
s q u a r e d é p e n d a n c e of intensity on b u n c h c h a r g e . M e a s u r e m e n t s a r e in p r o g r e s s to d e t e r m i n e t h e b u n c h
length f r o m t h e c o h e r e n t s p e c t r u m . A l r e a d y now, t h e
c o h e r e n t radiation intensity p r o v i d e s a g o o d signal for
efficient o p t i m i z a t i o n of t h e linac p h a s e s .
O p t i m i z a t i o n of linac a n d transferlines w a s c o m p l i c a t e d by persistent multipacting in t h e 5 0 0 M H z prebuncher, s i n c e t h e r e s p o n s i b l e c o m p a n y w a s not able
t o repair or r e p l a c e it d u r i n g 2 0 0 1 .
BOOSTER IMPROVEMENTS
C u r r e n t d e p e n d e n t b e a m l o s s e s on t h e b o o s t e r r a m p in
single b u n c h o p e r a t i o n lead to t h e c o n c l u s i o n , that t h e
head-tail instability d e s t r o y s t h e b e a m d u e t o a d r o o p
of c h r o m a t i c i t i e s d u r i n g a c c e l e r a t i o n f r o m s e x t u p o l a r
fields c r e a t e d by e d d y c u r r e n t s in t h e b e a m pipe [20].
P r o g r a m m i n g t h e w a v e f o r m s of t h e s e x t u p o l e p o w e r
supplies to compensate the calculated time-dependent
e d d y c u r r e n t s r e m o v e d this p r o b l e m .
Current-independent b e a m losses on the ramp
w e r e d u e to c r o s s i n g a third integer r e s o n a n c e , s i n c e
t h e t u n e originally w a s s w e e p i n g over a w i d e r a n g e (—>
f i g u r e 4 in [15]). Interactive editing of t h e q u a d r u p o l e
w a v e f o r m s kept t h e t u n e s c o n s t a n t at d e s i g n v a l u e s
over t h e w h o l e r a m p a n d t h u s a v o i d e d t h e s e losses.
T h e transfer efficiency f r o m b o o s t e r to s t o r a g e ring
a m o u n t s to 100 % at n o m i n a l ring chromaticities, red u c i n g to a p p r o x . 8 0 % at i n c r e a s e d c h r o m a t i c i t i e s for
s u p p r e s s i o n of t h e m u l t i - b u n c h instability [36].
CONCLUSION
T h e S L S s t o r a g e ring h a s b e e n c o m m i s s i o n e d to d e s i g n p e r f o r m a n c e well within t i m e s c h e d u l e .
Most
i m p o r t a n t p e r f o r m a n c e i s s u e s c o n c e r n i n g b e a m current, e m i t t a n c e , b e a m stability a n d lifetime h a v e b e e n
a c h i e v e d . T h e linear m a c h i n e is well u n d e r s t o o d a n d
c o r r e c t e d . A l s o t h e non-linear m a c h i n e s h o w s e x c e l lent a g r e e m e n t with theory. T h e investigation of collective effects is in p r o g r e s s .
The achievements on the performance are based
o n strict quality control for fabrication of m a g n e t s , girde r s a n d o t h e r c o m p o n e n t s , robust m e c h a n i c a l c o n c e p t s
a n d p r e c i s e a l i g n m e n t [37], reliable a n d flexible digital p o w e r s u p p l i e s [13], [14], rich a n d powerful d i a g nostic s y s t e m s including t u r n by t u r n B P M s [24] a n d
/xs-shutter c a m e r a s [26], flexible a n d powerful e n v i r o n m e n t s for m a c h i n e control a n d application d e v e l o p m e n t
[6], [7], [8], [16], a n d , last but not least, a high s e n s e of
responsibility f r o m all PSI e m p l o y e e s .
T h e S L S c o m m i s s i o n i n g w a s p r e s e n t e d at international e v e n t s [32], [33] a n d r e c e i v e d great a c k n o w l edgement from the accelerator community.
OUTLOOK
7 0 % of t h e 5 0 0 0 hrs of S L S o p e r a t i o n s c h e d u l e d for
2 0 0 2 a r e d e d i c a t e d to u s e r s . T h e r e m a i n i n g 3 0 % for
m a c h i n e d e v e l o p m e n t will b e d e v o t e d mainly t o t h e following t a s k s :
• f u r t h e r investigation of t h e m u l t i b u n c h instability a n d routine o p e r a t i o n of t h e t r a n s v e r s e multibunch feedback system,
• reoptimization of injection after r e p l a c e m e n t of
t h e linac s u b h a r m o n i c prebuncher,
• f u r t h e r m e a s u r e m e n t s a n d c o m p e n s a t i o n of linear a n d non-linear effects f r o m insertion d e v i c e s ,
• full o p e r a t i o n of t h e d y n a m i c a l i g n m e n t s y s t e m
[25], [34], [23], [38] including b e a m b a s e d B P M
calibration a n d b e a m b a s e d girder a l i g n m e n t ,
• c o m m i s s i o n i n g of t h e 3 r d h a r m o n i c s u p e r c o n d u c t i n g cavity [18] t o b e installed by J u n e ,
• i m p l e m e n t a t i o n a n d c o m m i s s i o n i n g of t h e fast
(100 Hz) orbit f e e d b a c k s y s t e m [2].
8
R E F E R E N C E S
[1] M. B ö g e , Update
on TRACY-2
SLS-TME-TA-1999-0002.
documentation,
[2] M. B ö g e et al., Fast Closed Orbit Control in
SLS Storage Ring, PAC'99, N e w York 1999.
the
[3] M. B ö g e , M. M u ñ o z , A. S t r e u n , Studies on imperfections in the SLS storage ring, EPAC'00, V i e n n a
2000.
[4] M. B ö g e , Beam position stabilization,
tific R e p o r t 2 0 0 1 , V o l u m e V I I .
PSI S c i e n -
[5] M. B ö g e , Measurement
and compensation
of linear optical distortions,
PSI Scientific R e p o r t 2 0 0 1 ,
Volume VII.
[6] M. B ö g e et al., Commissioning
of the SLS using CORBA beased Beam Dynamics
Applications,
PAC'01, Chicago 2 0 0 1 .
[7] M. B ö g e a n d J . C h r i n , On the Use of
CORBA
in High Level Software Applications
at the SLS,
ICALEPCS'01, San Jose 2 0 0 1 .
[8] M. B ö g e a n d J . C h r i n , On the Use of CORBA in
High Level Software Applications
at the SLS, PSI
Scientific R e p o r t 2 0 0 1 , V o l u m e V I I .
[9] D. Bulfone et al., Exploitation
of the
Integrated
Digital
Processing
and Analysis
of the ELETTRA/SLS
Transverse Multi-Bunch
Feedback
System, P A C ' 0 1 , C h i c a g o 2 0 0 1 .
[10] M. Dehler, Commissioning
results for the SLS
transverse
multi-bunch
feedback,
PSI Scientific
Report 2 0 0 1 , Volume VII.
[11] C. G o u g h a n d M. M a i l a n d , Septum and
Kicker
Systems for the SLS, P A C ' 0 1 , C h i c a g o 2 0 0 1 .
[12] G. Ingold a n d T. S c h m i d t , Insertion devices:
experiences,
PSI Scientific R e p o r t 2 0 0 1 ,
ume VII.
first
Vol-
[13] F. J e n n i a n d L. Tanner, Digitally Controlled
SLS
Magnet Power Supplies, P A C ' 0 1 , C h i c a g o 2 0 0 1 .
[14] F. J e n n i , Operating experience
with the SLS power
supplies, PSI Scientific R e p o r t 2 0 0 1 , V o l u m e V I I .
[15] W. J o h o , The SLS
mance,
booster
at its design
perfor-
PSI Scientific R e p o r t 2 0 0 0 , V o l u m e V I I .
[16] A. L ü d e k e , M. B ö g e , J . C h r i n , High level
software
and operator interface, PSI Scientific R e p o r t 2 0 0 1 ,
Volume VII.
[19] M. M u ñ o z , Top-up operation experience,
entific R e p o r t 2 0 0 1 , V o l u m e V I I .
PSI Sci-
[20] M. M u ñ o z a n d W. J o h o , Eddy current effects
SLS booster, S L S - T M E - T A - 1 9 9 8 - 0 0 1 0 .
[21] M. Pedrozzi, SLS pre-injector,
port 2 0 0 0 , V o l u m e V I I .
in the
PSI Scientific R e -
[22] L. Rivkin, First beam in the SLS storage
Scientific R e p o r t 2 0 0 0 , V o l u m e V I I .
ring, PSI
[23] V. Schlott, Results
from the horizontal
position
measurement
system, PSI Scientific R e p o r t 2 0 0 1 ,
Volume VII.
[24] V. Schlott et al., Commissioning
of the SLS
BPM System, P A C ' 0 1 , C h i c a g o 2 0 0 1 .
[25] V. Schlott et al., Dynamic
EPAC'00, Vienna 2000.
Alignment
at
Digital
SLS,
[26] V. Schlott et al.. SLS Linac Diagnostics
Commissioning Results, B I W ' 0 0 , C a m b r i d g e 2 0 0 0 .
[27] L. S c h u l z ,
provement,
ume VII.
Vacuum conditioning
and lifetime
imPSI Scientific R e p o r t 2 0 0 1 , Vol-
[28] C. S c h u l z e - B r i e s e , Protein crystallography,
Scientific R e p o r t 2 0 0 1 , V o l u m e V I I .
[29] B. S i n g h , Effects
dynamics
of SLS,
of insertion
devices
on the
PSI
beam
SLS-TME-TA-2001-0169.
[30] B. S i n g h a n d A. S t r e u n , Effects of insertion
devices on SLS beam dynamics,
PSI Scientific R e port 2 0 0 0 , V o l u m e V I I .
[31] G. S i n g h , Some SLS working points with lower
in bending
magneis,SLS-TME-TA-2001-0177.
ß
z
[32] A. S t r e u n et al., Commissioning
of the Swiss
Source, P A C ' 0 1 , C h i c a g o 2 0 0 1 .
Light
[33] A. S t r e u n et al., Commissioning
of the Swiss
Source, S S I L S ' 0 1 , S h a n g h a i 2 0 0 1 .
Light
[34] A. S t r e u n et al., Beam Stability
and Dynamic
Align-
ment at SLS, S S I L S , S h a n g h a i 2 0 0 1 .
[35] A. S t r e u n , Beam lifetime in the SLS storage
SLS-TME-TA-2001 -0191.
ring,
[36] A. S t r e u n , SLS booster-to-ring
transferline
optics for optimum injection efficiency,
SLS-TME-TA2002-0193.
[37] F. W e i , Results of survey and alignment,
entific R e p o r t 2 0 0 1 , V o l u m e V I I .
PSI Sci-
[17] P. M a r c h a n d et al., Operation
of the SLS
storage
ring RF system, PSI Scientific R e p o r t 2 0 0 1 , Volume VII.
[38] S. Z e l e n i k a et al., The SLS storage ring
support
and alignment systems, N I M A 4 6 7 - 4 6 8 (2001) 9 9 .
[18] P. M a r c h a n d et al., SLS third harmonic
superconducting RF system,
PSI Scientific R e p o r t 2 0 0 1 ,
Volume VII.
S L S annual reports, internal reports and conference contributions may be obtained from http://slsbd.psi.ch/pub/slsnotes
9
BEAM DYNAMICS STUDIES ON AN EXTENSION OF SLS FOR GENERATION OF
SUB-PICOSECOND X-RAY PULSES
A. Streun,
We will describe
a basic
of the SLS storage
for emission
aperture
ring:
of short
degradation
of the modulator
layout
B. Singh,
for an insertion
It consists
beam
to produce
of a modulator
( < 100 fs) X-ray pulses.
and vertical
G. Singh, G. Ingold, V. Schlott
emittance
and halo formation
wiggler
Results
increase
will be
sub-picosecond
for laser
beam
of calculations
will be presented.
optical
slicing
pulses
in one
and a radiator
on side-effects
Open problems
straight
undulator
concerning
dynamic
concerning
guiding
discussed.
lator U 1 7 ( 1 1 7 p e r i o d s of 17 m m , L O T p e a k field,
INTRODUCTION
4 m m g a p ) [2],
T h e t e c h n i q u e of b e a m slicing d e m o n s t r a t e d earlier at
A L S [7], u s e s a s h o r t - p u l s e ( f e m t o s e c o n d range) laser
• vertical m a g n e t c h i c a n e m a d e f r o m t w o vertically
to m o d u l a t e t h e e n e r g y of t h e e l e c t r o n s in a thin slice of
d e f l e c t i n g d i p o l e pairs, b r a c k e t i n g t h e modulator,
t h e b u n c h d u r i n g interaction inside a wiggler, c a l l e d "the
in o r d e r to c r e a t e vertical d i s p e r s i o n for spatial
m o d u l a t o r " . Variation of d i s p e r s i o n t h e n t r a n s l a t e s t h e
s e p a r a t i o n of e n e r g y - m o d u l a t e d b e a m s l i c e s in
e n e r g y m o d u l a t i o n into a spatial (horizontal or t r a n s -
t h e radiator,
v e r s e ) s e p a r a t i o n , t h u s e x t r a c t i n g t w o s m a l l satellite
b e a m s (of positive a n d n e g a t i v e e n e r g y deviation) f r o m
the core beam.
In a s u b s q u e n t undulator, c a l l e d "the
radiator", all b e a m s emit s y n c h r o t r o n radiation.
T h e ¿ í X A S b e a m l i n e p l a n n e d for S L S [6] will prov i d e a point to point m i c r o f o c u s o p t i c s for i m a g i n g t h e
radiation s o u r c e to t h e e x p e r i m e n t , a n d t h u s is suitable
•
additional f o c u s s i n g for p r o v i d i n g foci both in t h e
m o d u l a t o r and in t h e radiator in o r d e r to k e e p t h e
b e a m s m a l l e n o u g h to avoid l o s s e s at t h e w i g g l e r
a n d u n d u l a t o r g a p s a n d for m a t c h i n g t h e e l e c t r o n
b e a m ' s p h a s e s p a c e to t h e p h o t o n b e a m ' s diffraction phase space.
to extract t h e s h o r t p u l s e s f r o m t h e spatially s e p a r a t e d
A d d i n g f o c u s s i n g to o n e straight r e d u c e s t h e m a c h i n e
satellite b e a m s .
T h e r e f o r e , t h e F E M T O - b e a m l i n e will
periodicity f r o m 3 to 1 , t h u s d e s t r o y i n g t h e s e x t u p o l e
b e d e v e l o p e d in c o n j u n c t i o n w i t h a n d a s a f u r t h e r ex-
p a t t e r n , carefully b a l a n c e d to p r e s e r v e t h e r e q u i r e d dy-
t e n s i o n of t h e ¿ í X A S b e a m l i n e in s e c t o r 5 of t h e S L S .
namic aperture while performing the necessary chro-
F E M T O is e x p e c t e d to b e c o m e o p e r a t i o n a l late 2 0 0 4 ,
maticity c o r r e c t i o n s [1]. T h e distortion of m a c h i n e s y m -
i.e. o n e y e a r after c o m m i s s i o n i n g of t h e ¿ í X A S b e a m -
m e t r y h o w e v e r c a n b e m i n i m i z e d by a p p l i c a t i o n of t h e
line.
s o - c a l l e d "71-trick": All o p t i c s m o d i f i c a t i o n s a r e c o n f i n e d
A n o v e r v i e w of c o n c e p t s a n d e x p e c t e d p e r f o r m a n c e
b e t w e e n s e x t u p o l e pairs in t h e a r c s a d j a c e n t to t h e
H e r e , w e will report only
straight 5 L . T h e r e f o r e no optical f u n c t i o n at a n y sex-
o n t h e b e a m d y n a m i c s a s p e c t s t r e a t e d in 2 0 0 1 , c o n -
t u p o l e will b e affected. T h e b e t a t r o n p h a s e a d v a n c e s
cerning studies on how the proposed insertions can be
i n t r o d u c e d by t h e m o d i f i c a t i o n a r e exactly
i m p l e m e n t e d into t h e S L S s t o r a g e ring a n d h o w they
horizontally a n d
is given e l s e w h e r e [2], [3].
affect t h e s t o r e d b e a m .
= tt vertically.
=
0
S i n c e in a r e g u -
lar ( n o n - s k e w ) lattice all n o r m a l m u l t i p o l e s c o n t a i n only
e v e n p o w e r s of t h e vertical c o o r d i n a t e y, t h e n o n - l i n e a r
CONCEPTUAL DESIGN
T h e S L S s t o r a g e ring h a s t h r e e long straight s e c t i o n s of
11.76 m g r o s s length: straight 1L is u s e d for injection,
b e a m d y n a m i c s r e m a i n s basically u n c h a n g e d [12].
Basic layout
9 L for t h e U E 2 1 2 t w i n undulator, a n d 5 L , still empty, is
Figure
d e s i g n a t e d to b e u s e d for t h e ^ X A S / F E M T O i n s e r t i o n s .
straight 5 L b e t w e e n t h e a d j a c e n t s e x t u p o l e s S L B - 0 4
1 shows
and SLB-05:
Concept
P r e s e n t i n s e r t i o n d e v i c e s w e r e e x p e c t e d to affect t h e
b e a m only little in t e r m s of orbit d i s t o r t i o n , t u n e shifts
and dynamic aperture deterioration (causing reduced
lifetime a n d injection efficiency) [8]. O n g o i n g c o m m i s s i o n i n g of t h e i n s e r t i o n s installed s o far, c o n f i r m s this
e x p e c t a t i o n [4].
Installation of t h e F E M T O i n s e r t i o n w a s e x p e c t e d to
b e c o m e m o r e c h a l l e n g i n g , s i n c e t h e following e l e m e n t s
m o d u l a t o r w i g g l e r W 1 1 0 (18 p e r i o d s of 110 m m ,
2.5 T p e a k field, 7.5 m m gap) a n d radiator u n d u -
corresponding
modification
of
T h e central q u a d r u p o l e triplet a n d in-
c r e a s e d s t r e n g t h s of t h e existing d o u b l e t s at e n t r y a n d
exit p r o v i d e t h e additional f o c u s s i n g .
The asymmet-
ric c h i c a n e , b r a c k e t i n g t h e modulator, w a s d e s i g n e d
to c r e a t e a p u r e spatial s e p a r a t i o n (i.e.
suppress-
ing a n y additional a n g u l a r s e p a r a t i o n ) of t h e satellite
b e a m s . A s s u m i n g a laser p e r f o r m a n c e p r o v i d i n g a n e n e r g y m o d u l a t i o n of ± 1 3 M e V [2], a vertical d i s p e r s i o n
of 8.8 m m c r e a t e d in t h e radiator is suitable to s e p a r a t e
t h e satellites by
h a v e to b e i n s e r t e d into t h e straight:
•
the
Ay
with S
y
= ±48¿iin =
±5S
y
t h e r m s p h o t o n b e a m height ( d o m i n a t e d by
diffraction) [5], a n d t h e factor 5 a criterion for sufficient
s e p a r a t i o n f o u n d at A L S [7].
10
Belafunctions [ml
• 1 0
X/dP (ml
• 0. 0
DisDersion of stored beam
BetaY
/
. Dispersion Df satellite beams
|.I
/
•2
\ , . BetaX
-4
QGm QHm VB1 VB2 Modulator VB3 VB4 Qm Qc Qr
"--i
Chicane magnets
Radiator
QGr QHr
NI/
Triplet
F i g . 1 : M i n i - b e t a lattice with c h i c a n e for p u r e spatial
b e a m s e p a r a t i o n . T h e m o d u l a t o r W 1 1 0 a n d t h e radiator U 1 7 are installed in t h e long straight s e c t i o n 5L.
T h e total length of t h e lattice s e c t i o n s h o w n a m o u n t s to
14.84 m.
Dynamic aperture
T h e lattice modification a l o n e (i.e. e x c l u d i n g the m o d ulator a n d radiator fields) virtually d o e s not affect at all
t h e d y n a m i c a p e r t u r e of the m a c h i n e , t h u s p r o v i n g that
t h e 'V-trick" w o r k s . M a r g i n a l deteriorations are d u e t o a
slight i n c r e a s e of t h e total integrated s e x t u p o l e s t r e n g t h
(for c o m p e n s a t i o n of the additional chromaticity c r e a t e d
by t h e additional f o c u s s i n g ) a n d d u e to a deviation of
A$
f r o m 7T for particles with large m o m e n t u m deviat i o n s of \Ap/p\ > 6 % (which is b e y o n d the e n e r g y acc e p t a n c e in any c a s e ) .
y
Detailed tracking s t u d i e s w e r e m a d e to predict the
d y n a m i c a p e r t u r e d e c r e a s e a n d t o investigate the different c o n t r i b u t i o n s [9]: S i n c e t h e b e a m is relatively
w i d e inside the m o d u l a t o r a n d t h e radiator, t h e r e w a s
s o m e c o n c e r n , that the d y n a m i c a p e r t u r e will b e aff e c t e d by the horizontal off-axis field d e c r e a s e d u e to
t h e finite pole w i d t h . Also, t h e c h i c a n e m a g n e t s d e s i g n
including their multipole c o n t e n t s a n d realistic a s s u m p tions o n t h e field e r r o r s of the insertion d e v i c e s w e r e
i n c l u d e d . T h e c a l c u l a t i o n s did not s h o w significant dyn a m i c a p e r t u r e d e g r a d a t i o n for ideal insertion d e v i c e s
with pole w i d t h s a s p l a n n e d . After application of realistic field errors, a 10 % d e c r e a s e of t h e horizontal
a p e r t u r e w a s f o u n d . A possible i m p a c t on injection effic i e n c y h a s to be s t u d i e d further.
Emittance increase
T h e vertical e m i t t a n c e p r o d u c t i o n f r o m t h e c h i c a n e vertical d i p o l e s a m o u n t s t o 0.6 p m r a d , T h i s contribution
is negligible c o m p a r e d t o the « 2 5 p m - r a d f r o m other
lattice imperfections. T h u s , the c h i c a n e m a g n e t s c o u l d
be m a d e s t r o n g e r if larger s e p a r a t i o n is r e q u i r e d - a s
long a s t h e available s p a c e is sufficient. T h e p r e s e n t
layout c o n t a i n s c h i c a n e m a g n e t s of 30 c m length with
a m a x i m u m field of 0.43 T.
Modulator beam
T h e d i s p e r s i o n b u m p c a u s e s a n equivalent orbit excursion e x t e n d i n g u p t o 16 m m inside t h e modulator, s e e
figure 1. T h u s , the m o d u l a t o r h a s to b e e l e v a t e d a n d
p i t c h e d in o r d e r t o g u i d e the electron b e a m t h r o u g h its
n a r r o w gap. T h i s , however, c a u s e s the p h o t o n b e a m
of the m o d u l a t o r t o p r o p a g a t e at a vertical a n g l e of
- 4 . 5 m r a d a n d to finally hit t h e m a g n e t array of the radiator, w h i c h will be a m i n i - g a p i n - v a c u u m undulator.
S i n c e t h e m o d u l a t o r b e a m will c o n t a i n a p p r o x . 10 k W
of X - r a y s , this solution is u n a c c e p t a b l e . M o d i f i e d layo u t s have b e e n s u c c e s s f u l l y d e v e l o p e d [10] in o r d e r to
i n c r e a s e t h e m o d u l a t o r b e a m a n g l e in o r d e r t o s t o p it
before r e a c h i n g the radiator. However, t h e s e layouts
lead t o a n e n t a n g l e m e n t of orbit a n d f o c u s s i n g , w h i c h
c o m p l i c a t e s m a c h i n e o p e r a t i o n . F u r t h e r m o r e , it w o u l d
be desirable to g u i d e t h e m o d u l a t o r b e a m out of the
ring instead of d u m p i n g it, s i n c e it m a y be useful for exp e r i m e n t s too. Further w o r k is in p r o g r e s s t o evaluate
t h e b e s t option.
Beam halo
After travelling t h r o u g h t h e radiator, t h e satellite b e a m
slices will stretch (due to m o m e n t u m c o m p a c t i o n ) , filam e n t a n d slowly m e r g e with t h e c o r e b e a m t h r o u g h radiation d a m p i n g . In the m e a n t i m e they will f o r m a halo,
w h i c h m a y disturb other u s e r s a n d provide substantial
b a c k g r o u n d to s u b s e q u e n t laser s h o t s for the F E M T O driven e x p e r i m e n t . Prelimary s t u d i e s indicate, that the
d i s t u r b a n c e of other u s e r s will b e negligible.
T h e b a c k g r o u n d c a n be s u p p r e s s e d , if for e a c h interaction of t h e laser with the electron b e a m the laser
is s y n c h r o n i z e d t o a n e w b u n c h (out of a p p r o x . 4 0 0
b u n c h e s stored) a n d if the e x p e r i m e n t is g a t e d d u r i n g
t h e laser pulse. G i v e n a laser repetition rate of less
t h a n 10 k H z , t h e halo will d a m p d o w n c o m p l e t e l y f r o m
o n e s h o t to t h e next [11 ]. If t h e m a c h i n e o p e r a t e s in a
c a m s h a f t m o d e with o n e or a few h i g h - c h a r g e b u n c h e s
f r e q u e n t l y sliced a n d a l o w - c h a r g e train s e r v i n g other
e x p e r i m e n t s , a n e q u i l i b r i u m halo will f o r m . A n e s t i m a t e
of t h e b a c k g r o u n d signal f r o m this halo r e q u i r e s f u r t h e r
studies.
Diagnostics
M o m e n t u m c o m p a c t i o n of t h e a r c s will i n c r e a s e (resp.
d e c r e a s e ) the t i m e of flight of t h e satellite with positive
(resp. negative) e n e r g y c h a n g e . T h u s , at the e n t r a n c e
of the central 14° dipole B X - 0 5 in t h e T B A following the
straight 5L, t h e satellites will have a t e m p o r a l s p a c i n g
of ± 5 0 fs with a c o r r e s p o n d i n g dip in t h e c o r e b e a m bet w e e n . First s i m u l a t i o n s have s h o w n , that t h e c o h e r e n t
far-infrared (FIR) radiation (A > 30/xm) f r o m this t i m e
s t r u c t u r e will p e a k out f r o m t h e i n c o h e r e n t b a c k g r o u n d
f r o m t h e c o r e b e a m , a n d t h u s provide an excellent tool
for optimization of m a t c h i n g , a l i g n m e n t , laser s y n c h r o nisation, etc. T h e r e f o r e , the d i a g n o s t i c s b e a m l i n e at
t h e dipole B X - 0 5 will be e x t e n d e d by a FIR p a t h t o exploit t h e c o h e r e n t s y n c h r o t r o n radiation.
11
CONCLUSION AND OUTLOOK
A basic layout h a s b e e n f o u n d to realize t h e F E M T O
insertion for c r e a t i o n of s u b - p i c o s e c o n d optical p u l s e s
in o n e long straight of t h e S L S s t o r a g e ring.
Dyn a m i c a p e r t u r e c a l c u l a t i o n s indicate compatibility with
t h e g e n e r a l m a c h i n e p e r f o r m a n c e . T h e p r o b l e m of halo
f o r m a t i o n f r o m u s e d satellite b e a m s a n d the p r o b l e m
of g u i d i n g out or blocking t h e s t r o n g radiation f r o m the
m o d u l a t o r w i g g l e r require further investigations in o r d e r
to provide a c o m p l e t e proof of feasibility f r o m the b e a m
d y n a m i c s point of view.
REFERENCES
[ I ] J . B e n g t s s o n et al., Increasing
the energy
tance of high brightness
synchrotron
light
rings, N I M A 4 0 4 (1998) 2 3 7 .
accepstorage
[2] G. Ingold et al., Sub-picosecond
optical pulses
the SLS storage ring, P A C ' 0 1 , C h i c a g o 2 0 0 1 .
at
[3] G. Ingold et al.,
Conceptual
design:
subpicosecond
hard X-ray source, PSI Scientific R e port 2 0 0 1 , V o l u m e V I I .
[4] G. Ingold a n d T. S c h m i d t , Insertion devices: first experiences,
PSI Scientific R e p o r t 2 0 0 1 , V o l u m e V I I .
[5] W. J o h o , Radiation properties
TME-TA-1995-0004.
of an undulator,
SLS-
[6] A. S c h e i d e g g e r , D.Grolimund et al. Layout of the micro XAS beamline:
design study, PSI Scientific R e port 2 0 0 1 , V o l u m e V I I .
[7] R.W. S c h o e n l e i n et al., Generation
of
Femtosecond Pulses
of Synchrotron
Radiation,
Science
2 8 7 (2000) 2 2 3 7 a n d A p p l . Phys. B71 (2000) 1 .
[8] B. S i n g h , Effects of insertion devices on the
dynamics of SLS, S L S - T M E - T A - 2 0 0 1 - 0 1 6 9 .
beam
[9] B. S i n g h , SLS storage
ring non-linear
dynamics
with FEMTO insertion in one straight section, S L S TME-TA-2001-0181.
[10] G. S i n g h , FEMTO:
TME-TA-2001-0179.
Modification
of Layout,
SLS-
[ I I ] G. S i n g h , FEMTO: Preliminary
studies on effects
of background
electron pulses, S L S - T M E - T A - 2 0 0 1 0180.
[12] Y. W u et al., Mini-Beta
Lattice for the
Femtosecond X-Ray Source at the ALS, EPAC'OO, V i e n n a
2000.
12
ON THE USE OF CORBA IN HIGH LEVEL BEAM DYNAMICS APPLICATIONS
M. Böge,
J.
Chrin
Beam dynamics
(BD) applications
at the SLS have benefitted
from a distributed
computing
environment
in
which the Common Object Request Broker Architecture
(CORBA) forms the middleware
layer and
access
point to several different software components
for use in building high level software applications
at the
SLS. A suite of remote CORBA server objects provides the client with a convenient
and uniform
interface
to the CDEV (Common DEVice) controls library, the TRACY accelerator
physics package,
the Oracle database and an event logging facility. Use is made of methods provided
by the CORBA Portable
Object
Adaptor (POA) for accessing
ORB functions,
such as object reactivation
and object persistence,
the Implementation
Repository
(IMR) for the automatic reactivation
of servers, and the CORBA Event Service for
the propagation
of controls and physics data. An account of the CORBA framework,
as used by
applications in the commissioning
and first operation of the SLS, is
presented.
MOTIVATION
CORBA ARCHITECTURE
S e v e r a l high-level b e a m d y n a m i c s ( B D ) a p p l i c a t i o n s
h a v e b e e n d e v e l o p e d for t h e o p e r a t i o n a n d m o n i t o r i n g
of t h e S L S a c c e l e r a t o r facilities. Fig. 1 c a p t u r e s typical
c o m p o n e n t s r e q u i r e d by B D applications. T h e i r n u m ber a n d d e m a n d o n c o m p u t e r r e s o u r c e s m o t i v a t e d , in
part, a d e s i r e for a distributed c o m p u t i n g e n v i r o n m e n t .
T o this e n d , t h e C o m m o n O b j e c t R e q u e s t B r o k e r
( C O R B A ) [1], a n e m e r g i n g s t a n d a r d for distributed
object c o m p u t i n g ( D O C ) , h a s b e e n e m p l o y e d . Its u s e
at t h e S L S h a s a l l o w e d us t o realize t h e potential
benefits of distributed c o m p u t i n g a n d t o s i m u l t a n e o u s l y exploit f e a t u r e s inherent to C O R B A , s u c h a s t h e
interoperability b e t w e e n o b j e c t s , i m p l e m e n t e d in different l a n g u a g e s a n d on different p l a t f o r m s . C o m p l e x
t a s k s , s u c h a s t h e m o d e l l i n g of t h e S L S a c c e l e r a t o r s ,
c a n t h u s b e h a n d l e d by d e d i c a t e d c o m p u t e r s a n d d e v e l o p e d into r e u s a b l e c o m p o n e n t s w h i c h c a n b e acc e s s e d t h r o u g h r e m o t e m e t h o d invocations. D e v e l o p ing t h e entire suite of B D c o m p o n e n t s as C O R B A o b j e c t s , further e l e v a t e s t h e level at w h i c h a p p l i c a t i o n s
a r e d e s i g n e d a n d i m p l e m e n t e d . P l a t f o r m s hosting
high-level s o f t w a r e a p p l i c a t i o n s a r e no l o n g e r limited
to t h e libraries a n d e x t e n s i o n s available t o t h e host
o p e r a t i n g s y s t e m a s t h e introduction of a C O R B A
m i d d l e w a r e layer s e r v e s to extend
the developers
c h o s e n p r o g r a m m i n g l a n g u a g e . B D application d e v e l o p e r s are, h e n c e f o r t h , a b l e to f o c u s o n t h e s p e c i f i c s of
t h e application at h a n d , s u c h a s d e t e r m i n i n g userfriendly g r a p h i c a l interfaces, rather t h a n s t r u g g l e with
t h e intricate internals of n u m e r o u s a p p l i c a t i o n p r o g r a m
interfaces.
T h e m o s t f u n d a m e n t a l c o m p o n e n t of C O R B A is t h e
O b j e c t R e q u e s t B r o k e r ( O R B ) w h o s e t a s k is to facilitate c o m m u n i c a t i o n b e t w e e n o b j e c t s . G i v e n a n Intero p e r a b l e O b j e c t R e f e r e n c e ( I O R ) , t h e O R B is a b l e to
locate t a r g e t o b j e c t s a n d t r a n s m i t d a t a t o a n d f r o m
r e m o t e m e t h o d invocations. T h e interface t o a
C O R B A o b j e c t is s p e c i f i e d using t h e C O R B A Interface
Definition L a n g u a g e (IDL). A n IDL c o m p i l e r t r a n s l a t e s
t h e IDL definition into a n application p r o g r a m m i n g lang u a g e , s u c h a s C + + or J a v a , g e n e r a t i n g IDL s t u b s
a n d s k e l e t o n s that provide t h e f r a m e w o r k for clients i d e a n d s e r v e r - s i d e p r o x y c o d e , respectively. C o m p i lation of a p p l i c a t i o n s incorporating IDL s t u b s p r o v i d e s
a s t r o n g l y - t y p e d Static Invocation Interface (Sil). C o n versely, a m o r e flexible c o m m u n i c a t i o n m e c h a n i s m
c a n b e e s t a b l i s h e d t h r o u g h t h e u s e of t h e D y n a m i c
Invocation Interface (DM) a n d t h e D y n a m i c S k e l e t o n
Interface (DSI) allowing o b j e c t s to b e c r e a t e d w i t h o u t
prior k n o w l e d g e of t h e IDL interface. In s u c h c a s e s , a
d e s c r i p t i o n of t h e interface is retrieved at r u n t i m e f r o m
a n Interface R e p o s i t o r y (IFR), a d a t a b a s e c o n t a i n i n g
t h e pertinent m e t a d a t a . R e q u e s t s a n d r e s p o n s e s b e t w e e n o b j e c t s a r e d e l i v e r e d in a s t a n d a r d f o r m a t d e f i n e d by t h e Internet I n t e r - O R B Protocol (MOP), a
communications
protocol w h i c h a d h e r e s to t h e
C O R B A G e n e r a l I n t e r - O R B Protocol ( G I O P ) s p e c i f i cation a n d , a s s u c h , a c t s a s t h e b a s e for C O R B A interoperability o n t h e internet. R e q u e s t s a r e m a r s h a l l e d
in a platform i n d e p e n d e n t f o r m a t , by t h e client s t u b (or
in t h e DM), a n d u n m a r s h a l l e d o n t h e s e r v e r - s i d e into a
platform specific f o r m a t by t h e IDL s k e l e t o n (or in t h e
D S I ) a n d t h e o b j e c t adaptor, w h i c h s e r v e s as a m e diator b e t w e e n a n object's i m p l e m e n t a t i o n , t h e servant, a n d its O R B , t h e r e b y d e c o u p l i n g user c o d e f r o m
O R B p r o c e s s i n g . In its m a n d a t o r y v e r s i o n , t h e Portable Object Adaptor (POA) provides C O R B A objects
with a c o m m o n set of m e t h o d s for a c c e s s i n g O R B
f u n c t i o n s , ranging f r o m user a u t h e n t i c a t i o n t o o b j e c t
activation a n d object p e r s i s t e n c e . It's m o s t basic task,
h o w e v e r , is to c r e a t e object r e f e r e n c e s a n d to disp a t c h O R B r e q u e s t s a i m e d at t a r g e t o b j e c t s t o their
r e s p e c t i v e s e r v a n t s . T h e c h a r a c t e r i s t i c s of t h e P O A
a r e d e f i n e d at c r e a t i o n t i m e by a set of P O A policies. A
s e r v e r c a n host a n y n u m b e r of P O A s , e a c h with its
o w n set of policies t o g o v e r n t h e p r o c e s s i n g of req u e s t s . A m o n g t h e m o r e a d v a n c e d f e a t u r e s of t h e
Fig. 1 : D O C c o m p o n e n t s s e r v i n g B D a p p l i c a t i o n s .
13
P O A is t h e s e r v a n t m a n a g e r w h i c h a s s u m e s t h e role
of reactivating s e r v e r o b j e c t s ( s e r v a n t s ) as t h e y are
r e q u i r e d . It also p r o v i d e s a m e c h a n i s m to s a v e a n d
restore an object's state. T h i s , c o u p l e d with t h e u s e of
the I m p l e m e n t a t i o n R e p o s i t o r y ( I M R ) that h a n d l e s the
a u t o m a t e d start a n d restart of s e r v e r s , realizes object
persistency. B D a p p l i c a t i o n s are c o n s e q u e n t l y guara n t e e d the s e r v i c e s t h e y require [2].
ing S Q L s t a t e m e n t s h a v e b e e n p r o v i d e d that p e r f o r m
d a t a b a s e retrieval a n d m o d i f i c a t i o n o p e r a t i o n s . Interestingly, d a t a b a s e a c c e s s t h r o u g h the C O R B A interf a c e (with data m a r s h a l l i n g ) t a k e s half t h e t i m e t h a n
that t h r o u g h the J D B C A P I .
A C O R B A m e s s a g e server has been developed using
t h e U N I X syslog logging facility, profiting directly f r o m
t h e reliability of s t a n d a r d U N I X s e r v i c e s . R u n - t i m e
m e s s a g e s are s e n t to the logger with v a r i o u s priority
levels, the t h r e s h o l d for w h i c h c a n be a d j u s t e d dyn a m i c a l l y for a n y g i v e n servant.
S T O R A G E RING OPERATION
F i g . 2 : T h e C O R B A client-server a r c h i t e c t u r e .
Fig. 2 s h o w s t h e c o m p o n e n t s of the C O R B A a r c h i tectural m o d e l . T h e O R B c o r e is i m p l e m e n t e d a s a
r u n t i m e library linked into client-server a p p l i c a t i o n s .
A reactive, e v e n t - b a s e d , f o r m of p r o g r a m m i n g is a l s o
s u p p o r t e d by the C O R B A E v e n t Service w h i c h prov i d e s s e r v i c e s for the c r e a t i o n a n d m a n a g e m e n t of
C O R B A e v e n t c h a n n e l s . T h e s e m a y be u s e d by
CORBA
supplier/consumer
clients t o
propagate
e v e n t s a s y n c h r o n o u s l y on a p u s h or pull basis. Event
c h a n n e l s are c r e a t e d a n d registered with the C O R B A
N a m i n g Service, allowing clients t o obtain o b j e c t refe r e n c e s in the usual m a n n e r . C o m m u n i c a t i o n is
a n o n y m o u s in that the s u p p l i e r d o e s not require
k n o w l e d g e of the receiving c o n s u m e r s . T h e C O R B A
E v e n t Service h a s b e e n usefully e m p l o y e d in t h e
m o n i t o r i n g of h a r d w a r e d e v i c e s a n d in the distribution
of recalibrated data t o client c o n s u m e r s .
SERVER SYNOPSIS
Several o b j e c t s , typically of persistent type, h a v e b e e n
d e v e l o p e d u s i n g t h e C O R B A p r o d u c t M I C O [3], a fully
c o m p l i a n t i m p l e m e n t a t i o n of t h e C O R B A 2.3 s t a n d a r d .
T h e s e r v i c e s t h e s e o b j e c t s provide are briefly r e p o r t e d
here. A n e x p a n d e d d e s c r i p t i o n , t o g e t h e r with s p e c i f i c a t i o n s of t h e h a r d w a r e a n d s y s t e m c o m p o n e n t s of
the s e r v e r hosts, a p p e a r s e l s e w h e r e [4].
A d e d i c a t e d host r u n s the s e r v e r s that p e r f o r m t h e
c o m p u t e r intensive m o d e l l i n g of t h e S L S a c c e l e r a t o r s .
P r o c e d u r e s utilise the c o m p l e t e T R A C Y a c c e l e r a t o r
p h y s i c s library, e n a b l i n g clients to e m p l o y t e s t e d accelerator o p t i m i z a t i o n p r o c e d u r e s online.
T h e C D E V ( C o m m o n D E V i c e ) C + + c l a s s c o n t r o l s library p r o v i d e s the A P I to the E P I C S - b a s e d a c c e l e r a t o r
d e v i c e control s y s t e m . T h e C D E V s e r v e r s u p p l i e s
functionality for both s y n c h r o n o u s a n d a s y n c h r o n o u s
interactions with the control s y s t e m .
A d a t a b a s e s e r v e r p r o v i d e s a c c e s s to O r a c l e ins t a n c e s t h r o u g h the O r a c l e T e m p l a t e Library ( O T L )
a n d t h e O r a c l e Call Interface ( O C I ) . M e t h o d s e x e c u t -
S e v e r a l a p p l i c a t i o n s , written m a i n l y in T c l / T k or J a v a ,
h a v e b e e n s u c c e s s f u l l y i n t r o d u c e d for the c o m m i s s i o n i n g a n d o p e r a t i o n of the S L S b o o s t e r a n d s t o r a g e
rings [5], m a k i n g a m p l e u s e of t h e C O R B A f r a m e w o r k
provided. Server objects were extensively tested
t h r o u g h invocations initiated by a variety of client proce s s e s . O p e r a t o r intervention w a s m i n i m a l . Clients
w e r e able t o interact s p o n t a n e o u s l y with the m a n y
s e r v e r s a n d to display their e v e n t data. T h i s is e x e m plified by the s l o w global orbit f e e d b a c k s y s t e m (3 Hz
s a m p l i n g rate), w h i c h is both a c o n s u m e r t o e v e n t
g e n e r a t e d d a t a a n d a party to r e m o t e m e t h o d s invoc a t i o n s o n a variety of s e r v e r s .
CONCLUSION
T h e C O R B A m i d d l e w a r e h a s s e r v e d to e x t e n d the
capabilities of the p r o g r a m m i n g l a n g u a g e s u s e d by
B D application d e v e l o p e r s , t h e r e b y elevating t h e level
at w h i c h high-level s o f t w a r e a p p l i c a t i o n s are d e s i g n e d
a n d i m p l e m e n t e d . T h e p o w e r a n d flexibility of the
P O A , c o u p l e d with t h e s e r v e r activation r e c o r d s s t o r e d
within the IMR, h a s b e e n exploited to provide a robust
a n d m o d u l a r C O R B A b a s e d client-server f r a m e w o r k .
T h e m o d e l h a s b e e n p r o v e d t o be both reliable a n d
stable by the m a n y a p p l i c a t i o n s d e p l o y e d in the c o m m i s s i o n i n g a n d first o p e r a t i o n of t h e S L S .
REFERENCES
[1]
CORBA, http://www.omg.org/
[2]
M. B ö g e ,
J. Chrin,
SLS-TME-TA-2001-0183,
http://slsbd.psi.ch/pub/slsnotes/
[3]
MICO, http://www.mico.org/
[4]
M. B ö g e ,
J. Chrin,
SLS-TME-TA-2000-0162,
http://slsbd. psi . c h / p u b / s l s n o t e s /
[5]
M. B ö g e , J . C h r i n , M. M u ñ o z , A. S t r e u n , S L S - T M
E - T A - 2 0 0 1 - 0 1 8 2 , http://slsbd.psi.ch/pub/slsnotes/
14
VACUUM CONDITIONING AND LIFETIME IMPROVEMENT
L. Schulz,
A.
Streun
The ultra-high vacuum system of the SLS storage ring consists of a full antechamber
design with
stainless
steel vacuum chambers [1]. After an external bakeout at 250 °C the installation
under vacuum in the storage ring was completed
in 2000. The design values for the beam lifetime and the vacuum pressure
at
400 A could be achieved after half a year of
operation.
INTRODUCTION
T h e e l e c t r o n b e a m lifetime d e p e n d s s t r o n g l y o n t h e
p r e s s u r e in t h e ring v a c u u m s y s t e m . T h e v a c u u m
p r e s s u r e is d o m i n a t e d by t h e p h o t o d e s o r p t i o n of t h e
s y n c h r o t r o n light. T h e p h o t o n s w h i c h are s t o p p e d by
the p h o t o n a b s o r b e r s or t h e wall of t h e v a c u u m
c h a m b e r p r o d u c e p h o t o e l e c t r o n s with e n e r g i e s f r o m
s o m e 10 e V up to f e w K e V . T h e s e p h o t o e l e c t r o n s c a n
d e s o r b residual g a s m o l e c u l e s f r o m the c h a m b e r
w a l l s . T h e d e s o r p t i o n rate is t i m e d e p e n d e n t a n d dec r e a s e s as a f u n c t i o n of t h e a c c u m u l a t e d b e a m d o s e .
u s e d s h o w u n u s u a l correlations with t h e b e a m c u r r e n t
w h i c h are not s h o w n by t h e r e a d i n g s of the c o r r e s p o n d i n g sputter ion p u m p s . All g a u g e s are so called
active g a u g e s w h e r e t h e e l e c t r o n i c s is c o n n e c t e d d i rectly t o t h e s e n s o r . It s e e m s that t h e e l e c t r o n i c s of
t h e g a u g e s with b a d r e a d i n g s are sensitive to radiation. T h i s n e e d s , h o w e v e r , further investigation.
T h e highest p r e s s u r e r e a d i n g s (Fig. 1) c a n b e f o u n d in
t h e R F - c a v i t y straights, t h e injection straight a n d t h e
ID c h a m b e r s 0 4 S a n d 1 1 M . T h e a v e r a g e p r e s s u r e is
c a l c u l a t e d via t h e f o l l o w i n g e q u a t i o n :
VACUUM PRESSURE
<P>=
Total Pressure
T h e total p r e s s u r e in t h e S L S s t o r a g e ring is m o n i t o r e d with c o l d c a t h o d e g a u g e s . A l s o t h e p u m p current of t h e sputter ion p u m p s c a n be u s e d a s a n indication for the v a c u u m p r e s s u r e . T w o g a u g e s are installed in e a c h of the v a c u u m s e c t i o n s of the 12 m a g net a r c s . T h e 12 straight s e c t i o n s are e q u i p p e d w i t h
o n e or t w o g a u g e s .
Cavity 1+2
Cavity 3+4
ID-Chamber 11M
•
b ID-Chamber 04S
Injection Straight
•
•
H e r e i n is P¡ t h e p r e s s u r e m e a s u r e d with t h e individual
c o l d c a t h o d e g a u g e s . T h e f a c t o r F¡ is t a k e n f r o m the
m o d e l for the p r e s s u r e distribution [2] a n d r e p r e s e n t s
t h e ratio b e t w e e n t h e a v e r a g e p r e s s u r e a n d the c o r r e s p o n d i n g p r e s s u r e in t h e m o d e l at t h e position of t h e
g a u g e . AX,,
s t a n d s for the length of t h e v a c u u m s e c -
tion for w h i c h t h e p r e s s u r e r e a d i n g is r e p r e s e n t a t i v e .
D u e to the s y n c h r o t r o n - r a d i a t i o n driven g a s d e s o r p tion, the a v e r a g e p r e s s u r e is a linear f u n c t i o n of t h e
total b e a m current. T h e ratio b e t w e e n p r e s s u r e rise
a n d b e a m c u r r e n t d e c r e a s e s with i n c r e a s i n g t h e a c cumulated beam dose.
Fig. 2 s h o w s t h e e v o l u t i o n of t h e d y n a m i c p r e s s u r e
d P / d l as a f u n c t i o n of t h e a c c u m u l a t e d b e a m d o s e
w h i c h h a s t h e e x p e c t e d d e c r e a s e of - 2 / 3 ( s h o w n in
t h e plot with a d o u b l e l o g a r i t h m i c scale).
•
•
•
ZA
pressure P(s)
— average pressure <P>
50
100
150
200
250
300
s[m]
Fig. 1 : L o n g i t u d i n a l p r e s s u r e distribution after 100 A h
at 3 5 0 m A ; d a t a t a k e n in J u l y 2 0 0 1 .
Fig. 1 s h o w s a s n a p s h o t of t h e longitudinal distribution
of t h e total p r e s s u r e in t h e ring at a b e a m c u r r e n t of
3 5 0 m A a n d after an a c c u m u l a t e d b e a m d o s e of
100 A h .
In total, 3 9 c o l d c a t h o d e g a u g e s are installed in t h e
s t o r a g e ring. For t h e calculation of the a v e r a g e p r e s s u r e t h e r e a d i n g s of o n l y 30 g a u g e s c a n be u s e d .
H o w e v e r , 4 g a u g e s h a v e a g r o u n d short a n d c a n o n l y
be r e p l a c e d after v e n t i n g of the c o r r e s p o n d i n g v a c u u m s e c t i o n s . T h e o t h e r five g a u g e s w h i c h c a n n o t be
É
1.0E-07
10
Beam Dose [A h]
Fig. 2 : D y n a m i c p r e s s u r e d P / d l a s a f u n c t i o n of a c c u mulated beam dose.
15
T h e t e m p o r a r y i n c r e a s e o f t h e d y n a m i c p r e s s u r e in
Fig. 2 is c o r r e l a t e d w i t h v a c u u m s h u t d o w n s a n d t h e
installation of insertion d e v i c e c h a m b e r s .
N
2
Equivalent Pressure
R e l e v a n t for the b e a m lifetime is t h e residual g a s
c o m p o s i t i o n in t h e v a c u u m s y s t e m . D u e t o the q u a d ratic d e p e n d e n c y of t h e elastic s c a t t e r i n g
and
Bremsstrahlungs scattering gas c o m p o n e n t s with a
high a t o m i c m a s s n u m b e r Z h a v e a h i g h e r influence
o n t h e b e a m lifetime. T h e partial p r e s s u r e s for h y d r o gen ( P 2 7 0 % , Z=1) and carbon monoxide ( P o 3 0 % ,
Z = 7 ) are the m a i n c o n t r i b u t i o n s to t h e S L S v a c u u m .
H
S
C
s
T h e n i t r o g e n e q u i v a l e n t p r e s s u r e is better s u i t e d t h a n
the total p r e s s u r e t o s h o w t h e c o r r e l a t i o n b e t w e e n
b e a m lifetime a n d p r e s s u r e . Fig. 3 s h o w s t h e n i t r o g e n
e q u i v a l e n t p r e s s u r e a s a f u n c t i o n of t i m e w h i c h is
e x t r a p o l a t e d f r o m t h e v a l u e s for t h e d y n a m i c p r e s s u r e
and the corresponding base pressure and a beam
c u r r e n t of 4 0 0 m A .
m a c h i n e ' s e n e r g y a c c e p t a n c e d u e t o t h e large n e g a tive h o r i z o n t a l s e c o n d o r d e r c h r o m a t i c i t y . M o v i n g t h e
h o r i z o n t a l t u n e f r o m 2 0 . 3 8 to 2 0 . 4 2 i n c r e a s e d t h e
lattice e n e r g y a c c e p t a n c e f r o m a p p r o x . ± 2 % to ± 3 %
a n d t h u s d o u b l e d t h e lifetime.
V a r i a t i o n of R F v o l t a g e a n d c o m p a r i s o n w i t h t r a c k i n g
s t u d i e s a l l o w e d t o e s t i m a t e the vertical e m i t t a n c e t o
a p p r o x . 30 p m r a d , w h i c h is in a g r e e m e n t w i t h
ex-
p e c t a t i o n s a n d earlier d i f f e r e n c e orbit m e a s u r e m e n t s .
A v a r i a t i o n of t h e single b u n c h c u r r e n t i n d i c a t e d turb u l e n t b u n c h l e n g t h e n i n g b e y o n d a t h r e s h o l d of
1.1 m A per b u n c h . T h i s h o w e v e r n e e d s f u r t h e r i n v e s tigation.
B e y o n d 2.2 m A of single b u n c h current, a n e x t r a o r d i nary linear i n c r e a s e of p r e s s u r e w i t h c u r r e n t w a s o b s e r v e d , w h i c h is not c a u s e d by g a s d e s o r p t i o n , but
p r o b a b l y by m i c r o w a v e h e a t i n g of the v a c u u m c h a m ber.
jpr-^
B e a m D o s e [A h ]
% \ \
F i g . 3:
F i g . 4 : P r o d u c t of total b e a m lifetime a n d b e a m cur-
N 2 e q u i v a l e n t p r e s s u r e at a c u r r e n t of 4 0 0 m A
At t h e e n d of t h e c o m m i s s i o n i n g p h a s e , in t h e m i d d l e
of A u g u s t , after 6 m o n t h s of o p e r a t i o n , a v a l u e in t h e
r a n g e of 2-10" m b a r for the N e q u i v a l e n t p r e s s u r e at
400 m A was achieved.
9
2
B E A M LIFETIME
Total Lifetime
rent v s b e a m d o s e .
CONCLUSIONS
T h e d e s i g n v a l u e s for the v a c u u m p r e s s u r e a n d t h e
b e a m lifetime c o u l d be a c h i e v e d after 6 m o n t h s of o p e r a t i o n . T h e results s h o w that the c o n c e p t of t h e
s t a i n l e s s steel a n t e c h a m b e r d e s i g n w i t h e x t e r n a l
bakeout was successful.
S i m u l t a n e o u s l y w i t h t h e i m p r o v e m e n t of v a c u u m p r e s s u r e a l s o a n i n c r e a s e in t h e total lifetime of t h e elect r o n b e a m c o u l d b e o b s e r v e d . Fig. 4 s h o w s t h e prog r e s s i o n of the p r o d u c t of total b e a m lifetime a s a
f u n c t i o n of t h e a c c u m u l a t e d b e a m d o s e .
ACKNOWLEDGEMENTS
Analysis of Beam Lifetime
REFERENCES
S c r a p e r e x p e r i m e n t s p r o v e d the s q u a r e d e p e n d a n c y
of elastic s c a t t e r i n g g a s lifetime o n the s c r a p e r p o s i tion in g o o d a g r e e m e n t w i t h t h e o r y a n d a l l o w e d t o
calibrate t h e m e a s u r e d a v e r a g e p r e s s u r e .
[1]
L. S c h u l z , T. Bieri, N. Gaiffi, The SLS
Vacuum
System, PSI Scientific R e p o r t 2 0 0 0 , V o l u m e V I I .
[2]
G . H e i d e n r e i c h , L. S c h u l z , P. W i e g a n d ,
Vacuum
System for the Swiss Light Source, Proc. E P A C
1998.
[3]
A. S t r e u n , Beam Lifetime
in the SLS
Storage
Ring, S L S - T M E - T A - 2 0 0 1 - 0 1 9 1 , D e c e m b e r 2 0 0 1 .
After s u b t r a c t i n g of t h e elastic s c a t t e r i n g c o n t r i b u t i o n ,
the T o u s c h e k lifetime w a s i n v e s t i g a t e d a s f u n c t i o n of
v a r i o u s p a r a m e t e r s [3].
V a r i a t i o n of t h e b e t a t r o n t u n e s r e v e a l e d , t h a t t h e n o n s y s t e m a t i c t h i r d - i n t e g e r r e s o n a n c e 3 Q = 61 limits t h e
X
T h e a u t h o r s w o u l d like t o t h a n k the S L S c r e w w h o
h a v e i n c r e a s e d t h e total b e a m d o s e in m a n y long a n d
b o r i n g l a u n d r y shifts.
16
SLS THIRD HARMONIC SUPERCONDUCTING RF SYSTEM
P. Marchand,
M. Pedrozzi,
INTRODUCTION
P r e s e n t l y , t h e R F s y s t e m of t h e S L S s t o r a g e ring c o n sists of f o u r 5 0 0 M H z c o p p e r cavities t h a t c a n g e n e r ate a total R F v o l t a g e of 2.4 M V a n d deliver 2 4 0 k W t o
the b e a m . T h i s s y s t e m p r o v e d t o b e quite reliable in
o p e r a t i o n d u r i n g t h e y e a r 2 0 0 1 [1].
In o r d e r t o f u r t h e r i m p r o v e t h e b e a m lifetime, w h i c h is
d o m i n a t e d by T o u s c h e k s c a t t e r i n g , it is p l a n n e d t o
implement a complementary 3rd harmonic RF system
for l e n g t h e n i n g t h e b u n c h e s a n d t h e r e f o r e r e d u c i n g
their c h a r g e d e n s i t y [2]. S i n c e t h e b o u n d a r y c o n d i t i o n s
are similar t o t h o s e at E L E T T R A , t h e t w o institutes
decided to search for a c o m m o n approach. T h e chos e n solution is t h e u s e of a n idle s u p e r c o n d u c t i n g
s y s t e m b a s e d o n a "scaling t o 1.5 G H z " of t h e
3 5 0 M H z t w o - c e l l - c a v i t y d e v e l o p e d at S a c l a y f o r t h e
S O L E I L project [ 3 ] . In O c t o b e r 1 9 9 9 , P S I , S i n c r o t r o n e
Trieste and C E A Saclay concluded a collaboration
a g r e e m e n t , t h e s o - c a l l e d S U P E R - 3 H C Project, w i t h
the o b j e c t i v e of d e s i g n i n g a n d p r o d u c i n g t w o c o m p l e t e
c r y o m o d u l e s , o n e f o r E L E T T R A a n d o n e f o r S L S [4].
T h e cavity c o n s i s t s of t w o N b / C u cells, e n c l o s e d in
their L H e r e s e r v o i r s ; o n t h e t u b e b e t w e e n t h e t w o
cells a r e l o c a t e d t h e c o u p l e r s f o r t h e d a m p i n g of t h e
H i g h e r O r d e r M o d e ( H O M ) i m p e d a n c e s (Fig. 1). E a c h
cell is e q u i p p e d w i t h its o w n f r e q u e n c y tuner, a m e c h a n i c a l s y s t e m , d r i v e n by a s t e p p i n g m o t o r , w h i c h
c h a n g e s t h e cell l e n g t h within t h e limits of t h e elastic
d e f o r m a t i o n ( ± 5 0 0 k H z r a n g e , 10 H z a c c u r a c y ) . In t h e
idle cavity, t h e b e a m - i n d u c e d v o l t a g e (V ° c A f l
) is
directly c o n t r o l l e d v i a t h e f r e q u e n c y t u n e r s . W i t h a
cavity v o l t a g e of 8 0 0 k V (4 M V / m ) , o n e a n t i c i p a t e s a
b u n c h - l e n g t h e n i n g f a c t o r of a b o u t 3 a n d t h a t s h o u l d
result in 2 - 3 t i m e s longer b e a m lifetime.
b e a m
HOM DAMPING
In o r d e r t o p r e v e n t t h e e x c i t a t i o n of c o u p l e d b u n c h
instabilities, a n efficient d a m p i n g of all t h e cavity
H O M ' s is r e q u i r e d in a f r e q u e n c y r a n g e 1.5 - 3.6 G H z .
T h i s is a c h i e v e d by u s i n g six c o a x i a l H O M c o u p l e r s
(two f o r t h e longitudinal m o d e s , f o u r f o r t h e t r a n s v e r s e
m o d e s ) , l o c a t e d o n t h e t u b e c o n n e c t i n g t h e t w o cells
a n d a r r a n g e d a s s h o w n in Fig. 1 [ 5 ] . T h e o p t i m i s a t i o n
w a s p e r f o r m e d in t w o s t e p s : first, t h e "best" position of
the c o u p l e r s o n t h e t u b e w a s d e t e r m i n e d u s i n g t h e
c o m p u t e r c o d e U R M E L a n d t h e n t h e s e n s i t i v e parts of
the c o u p l e r s (A, B, C, D, E, F in Fig. 2 ) w e r e o p t i m i s e d
by " c u t a n d try iterations" o n a c o p p e r cavity m o d e l .
For t h e longitudinal (resp. t r a n s v e r s e ) m o d e s t h e loop
axis is parallel (resp. p e r p e n d i c u l a r ) t o t h e b e a m axis.
T h e m e a s u r e d i m p e d a n c e s after o p t i m i s a t i o n a r e
s h o w n in F i g . 3; o n l y o n e t r a n s v e r s e m o d e e x c e e d s
the s p e c i f i c a t i o n by a b o u t 1 5 % . M e a s u r e m e n t s o n t h e
model also demonstrated that the fundamental m o d e
rejection of t h e c o u p l e r s w a s large e n o u g h (> 2 0 d B ) .
However, computation with the HFSS code pointed
A. Anghel
(CRPP
Lausanne)
out t h a t it w a s quite s e n s i t i v e t o t h e filter g a p t o l e r a n c e
of t h e t r a n s v e r s e m o d e c o u p l e r s . A m e c h a n i s m f o r
a d j u s t i n g this p a r a m e t e r will t h e r e f o r e b e u s e d f o r
t u n i n g t h e final c o u p l e r s o n c e m o u n t e d o n t h e cavity.
Long. Mode couplers
Cavity He reservoir
Transv.
Mode
couplers
F i g . 1 : S U P E R - 3 H C cavity w i t h H O M c o u p l e r s .
A-Filter Line
B - Off-Axis Line
C - Axis Line
D - Stub
E - Gap Line
F - Capacitive Gap
F i g . 2 : S U P E R - 3 H C H O M coupler.
Requirements : Max. 7k.ÖhIH.GHJ^
Long, modes [kß.GHz]
6
4
2
0
2.47 2.53 2.61 2.69 2.83 2.98 3.08 3.18 3.36 3.59
160
Requirements : Max. 130 M / m
120 -
Transv. modes [kii/m]
40
0
.72 1.72 1.93 2.06 2.10 2.15 2.30 2.50 2.71 2.87
F i g . 3: Measured H O M impedances vs frequency.
CRYOGENIC SYSTEM
Fig. 4 s h o w s a s c h e m e of t h e c r y o m o d u l e c o o l i n g
system. T h e LHe from the dewar enters the cryomodule t h r o u g h a p h a s e s e p a r a t o r ( P S 1 ) . T h e t w o cavity
r e s e r v o i r s a r e t h e n filled w i t h L H e at 4 . 5 K f r o m t h e
17
b o t t o m ; t h e y are c o n n e c t e d o n t h e t o p by a c o m m o n
v e s s e l ( P S 2 ) , w h i c h r e c u p e r a t e s the cold G H e . Part of
this c o l d G H e is r e t u r n e d b a c k to the refrigerator w h i l e
the rest is u s e d t o cool t h e c o p p e r t h e r m a l shield
(65 K) a n d t h e t w o cavity e x t r e m i t y t u b e s (4.5 3 0 0 K). T h e inner t u b e a n d H O M c o u p l e r s are c o n d u c t i o n c o o l e d at 4.5 K. L a y e r s of s u p e r - i n s u l a t i o n ,
p l a c e d on the s h i e l d , r e d u c e t h e r a d i a t e d heat f r o m
the r o o m t e m p e r a t u r e parts. T h e m a x i m u m anticip a t e d c r y o g e n i c h e a t load of t h e different parts are
listed in T a b l e 1 (for V = 8 0 0 kV, l
= 400 mA).
Compressor
b e a m
T h e c r y o g e n i c s o u r c e is a H E L I A L 1 0 0 0 refrigeratorliquefier f r o m A I R L I Q U I D E . It c o n s i s t s of a s c r e w c o m p r e s s o r with oil r e m o v a l unit, a t u r b i n e - c o l d - b o x
and the associated control-command system. The
5 0 0 I d e w a r , the c r y o g e n i c transfer lines a n d t h e
v a l v e - b o x are a l s o parts of the A I R L I Q U I D E s u p p l y .
T h e s y s t e m is d e s i g n e d t o s i m u l t a n e o u s l y p r o v i d e (in
m i x e d m o d e ) m o r e t h a n 7.5 l/h of liquefaction d u t y
a n d 6 5 W of refrigeration p o w e r at 4 . 5 K. T h a t is 5 0 %
m o r e t h a n the a n t i c i p a t e d r e q u i r e m e n t ( T a b l e 1 ).
T h e o p e r a t i o n w i t h " w a r m c r y o m o d u l e " is c o n s i d e r e d
as a p o s s i b l e o p t i o n (in c a s e of c r y o - s o u r c e failure, for
instance). A t r o o m t e m p e r a t u r e , a l t h o u g h t h e cavity is
d e t u n e d a n d t h e i n d u c e d v o l t a g e is largely r e d u c e d ,
the b e a m c a n d e p o s i t a f e w 100 W into the cavity. T h e
c o l d - b o x is t h e n isolated ( v a l v e s L C V 5 a n d P C V 2
c l o s e d ) a n d the c o m p r e s s o r e n s u r e s a circulation of
" w a r m " G H e ; the lines "T" (inlet) a n d " S " (outlet) are
p r o v i d e d for this p u r p o s e . Line "T" is a l s o u s e d t o m i x
G H e with L H e a n d t h u s control t h e t e m p e r a t u r e of t h e
fluid at t h e input of the c r y o m o d u l e d u r i n g t h e c o o l d o w n p r o c e s s . For e a c h o p e r a t i o n m o d e , all t h e relev a n t v a l u e s of p r e s s u r e , L H e level, t e m p e r a t u r e , G H e
a n d L H e f l o w are either r e g u l a t e d or m o n i t o r e d by a
PLC, using the various sensors and controlled valves
of t h e s y s t e m .
Components
Load
2 R F cells
22 W
F i g . 4 : S c h e m e of t h e c r y o g e n i c s y s t e m .
0
2
4
F i g . 5: M e a s u r e d Q
0
6
8
10
12
(at 4 . 5 K) v s field for the 2 cells.
Comments
Directly in LHe bath
2 L-couplers
3 W
Cooled by conduction
4 T-couplers
8.5 W
Cooled by conduction
2 Extrem, tubes
Cryomodule
static losses
Cryo-lines
0.2 W
5.1 W
With 2 x 0.05 g/s cold GHe
With 0.071 g/s cold GHe
in thermal shield (65K)
6.5 W
Tot. refrigeration p o w e r at 4.5 K : 45.3 W
Tot. GHe f l o w : 1.171 g/s -> 5.2 l/h of liquefaction
T a b l e 1 : C r y o g e n i c load (4 M V / m , 4 0 0 m A , Q : 2 1 0 ) .
0
8
F i g . 6: C r y o m o d u l e a s s e m b l y (L = 1.1 m, 0 = 0.8 m ) .
PROJECT STATUS AND TIME SCHEDULE
T h e fabrication a n d c o l d t e s t s of the S L S cavity at
C E R N w e r e c o m p l e t e d in O c t o b e r . Fig. 5 s h o w s t h e
m e a s u r e d Q (at 4.5 K) v s a c c e l e r a t i n g field [6]. A t t h e
o p e r a t i n g field of 4 M V / m , Q is a b o u t 2.6 1 0 for both
cells. T h e o t h e r c o m p o n e n t s of t h e c r y o m o d u l e are
u n d e r f a b r i c a t i o n . T h e c o m p l e t e c r y o m o d u l e (Fig. 6 )
will be a s s e m b l e d a n d t e s t e d in F e b r u a r y - M a r c h at
S a c l a y . T h e delivery of the c r y o m o d u l e a s well a s the
c r y o - s o u r c e is s c h e d u l e d for April a n d t h e installation
in t h e S L S during the s h u t d o w n s of M a y / J u n e 2 0 0 2 .
REFERENCES
[1]
P. M a r c h a n d et al., P A C 9 9 , p. 9 8 6
Scientific Report 2 0 0 1 , V o l u m e V I I .
[2]
P. M a r c h a n d , P A C 9 9 , p. 9 8 9 .
[3]
S. C h e l et al., E P A C 2 0 0 0 , p. 2 0 4 6 .
[4]
M. S v a n d r l i k et al., E P A C 2 0 0 0 , p. 2 0 5 1 .
[5]
P. B o s l a n d et al., p r e s e n t e d at P A C 2 0 0 1 .
[6]
R. Losito, C E R N , private c o m m u n i c a t i o n .
0
0
8
and
PSI
18
BEAM POSITION STABILIZATION
M. Böge,
T.
Schilcher
As a first step towards the implementation
of a DSP based Fast Orbit Feedback operating at sampling
rates
of 4 KHz, a Slow Orbit Feedback has been implemented
which corrects orbits at rates < 3 Hz. It reuses
thoroughly
tested components
of the normal orbit correction application.
Short and long term orbit
stability
of < 1 \xm at the locations of the insertion devices has been achieved in the horizontal and vertical
plane.
Path-length
changes are adjusted using the RF frequency as an additional corrector within the SVD based
correction algorithm.
As a result a long term energy stability of dP/P « 2e-5 has been
obtained.
INTRODUCTION
It is vital for a s u c c e s s f u l user o p e r a t i o n to r e p r o d u c e
a n d stabilize a previously e s t a b l i s h e d reference orbit
("Golden Orbit") within 1/1 Oth of t h e vertical b e a m size
c o r r e s p o n d i n g to « 1 ¿¿m at the location of the insertion
d e v i c e s (IDs). A s a c o n s e q u e n c e , the digital B P M [1]
a n d c o r r e c t o r h a r d w a r e [2] have b e e n d e s i g n e d in
o r d e r to allow for the i m p l e m e n t a t i o n of a Fast Orbit
F e e d b a c k ( F O F B ) that is able to s u p p r e s s residual orbit
oscillations u p to « 100 Hz with a t t e n u a t i o n factors of
> 10 [3]. T h e F O F B i m p o s e s tight c o n s t r a i n t s o n the
capabilities a n d reliability of t h e involved s u b s y s t e m s
s i n c e the f e e d b a c k loop r u n s at a s a m p l i n g rate of
4 K H z on the D S P level of t h e B P M h a r d w a r e .
In o r d e r to gain e x p e r i e n c e with the v a r i o u s s u b s y s t e m s , a S l o w Orbit F e e d b a c k ( S O F B ) with m u c h
relaxed r e q u i r e m e n t s ( < 3 Hz c o r r e c t i o n rate) h a s
b e e n i m p l e m e n t e d , c o m m u n i c a t i n g with t h e u n d e r l y i n g
h a r d w a r e c o m p o n e n t s t h r o u g h a " C D E V Server" w h i c h
is c o n n e c t e d to t h e E P I C S b a s e d control s y s t e m [4, 5].
GLOBAL ORBIT CORRECTION AND SOFB
Global c l o s e d orbit c o r r e c t i o n in t h e S L S s t o r a g e ring
is b a s e d on t h e Singular Value D e c o m p o s i t i o n ( S V D )
t e c h n i q u e w h i c h m a k e s " M o s t Effective C o r r e c t o r "
a n d " M I C A D O " like long range c o r r e c t i o n s c h e m e s
o b s o l e t e . For t h e horizontal orbit c o r r e c t i o n it is crucial
to take into a c c o u n t p a t h - l e n g t h effects by c o r r e c t i n g
off-energy orbits with t h e R F frequency. T h e difference
of the original orbit a n d t h e S V D fitted off-energy part,
w i t h a deviation of d P / P c o r r e s p o n d i n g to a f r e q u e n c y
c h a n g e df, is s u b m i t t e d to the orbit c o r r e c t i o n .
S i n c e the b e g i n n i n g of the c o m m i s s i o n i n g ,
this
s c h e m e h a s b e e n s u c c e s s f u l l y a p p l i e d to p e r f o r m
o p e r a t o r i n d u c e d c o r r e c t i o n s . D u e to the m o d u l a r i t y
of the b e a m d y n a m i c s software e n v i r o n m e n t [6], thoro u g h l y t e s t e d software c o m p o n e n t s c o u l d be r e u s e d
to i m p l e m e n t a S l o w Orbit F e e d b a c k ( S O F B ) . In this
c a s e t h e o p e r a t o r is " r e p l a c e d " by a client p r o g r a m
" F e e d b a c k Client" w h i c h initiates an orbit c o r r e c t i o n at
a given f r e q u e n c y (see Fig. 1).
Console
Event @ 0.5Hz
CORBA Server
Event
® 2Hz
Model Server
F i g . 1 : S c h e m a t i c V i e w of t h e S O F B : the " F e e d b a c k
Client" on t h e " M o d e ! Server" level r e p l a c e s the o p e r a tor driven G U I "oco Client" o n the " C o n s o l e " level. T h e
client g e t s B P M d a t a f r o m t h e " B P M Server", a s k s the
" T R A C Y Server" for t h e c o r r e s p o n d i n g m o d e l p r e d i c t e d
c o r r e c t o r settings a n d a p p l i e s t h e c o r r e c t i o n t h r o u g h
t h e " C D E V Server".
ing over 6 4 orbit s a m p l e s , c o r r e s p o n d i n g to a n interval of 2 m s , it is possible to get " s t r o b o s c o p i c " position
r e a d i n g s at a rate of 3 Hz w i t h an error < 0.5 um. T h e
" B P M Server" in Fig. 1 monitors, collects a n d s e n d s the
B P M d a t a to t h e " F e e d b a c k Client" at 2 Hz. B P M s disa b l e d on the E P I C S level are a u t o m a t i c a l l y e x c l u d e d
f r o m the S O F B loop.
T h e s a m e h o l d s for c o r r e c t o r s w h i c h have r e a c h e d their m a x i m u m s t r e n g t h . T h e
" T R A C Y Server" p r e d i c t s a c o r r e c t o r p a t t e r n w h i c h res t o r e s the " G o l d e n Orbit" d e f i n e d by t h e "oco Client".
Finally, the " C D E V Server" a p p l i e s t h e p r o p o s e d correction, w h i c h is t o g g l i n g b e t w e e n the horizontal a n d
vertical p l a n e s . Fine t u n i n g of t h e f e e d b a c k loop is
d o n e t h r o u g h a low p a s s filter, c o r r e c t i n g on t h e avera g e over several s u c c e s s i v e B P M d a t a sets, a n d gain
a d j u s t m e n t . By default t h e S O F B a v e r a g e s over 3 d a t a
s e t s a n d a p p l i e s 7 5 % of t h e p r o p o s e d c o r r e c t i o n . T h u s
a full S O F B c y c l e t a k e s 3 s. It r e m a i n s to be a d d e d that
t h e S O F B r u n s only for o n e previously set B P M g a i n .
T h i s e n s u r e s that t r a n s i e n t s visible at c u r r e n t i n d u c e d
B P M gain c h a n g e s are not s e e n by t h e S O F B .
SOFB RESULTS
SOFB IMPLEMENTATION
For the S O F B the digital B P M s y s t e m is o p e r a t e d in a n
injection t r i g g e r e d " 2 5 0 m s r a m p e d m o d e " . By a v e r a g -
Fig. 2 d o c u m e n t s the p e r f o r m a n c e of t h e S O F B over
12 h o u r s of user o p e r a t i o n . After a c c u m u l a t i n g a current of 3 2 0 m A , t h e t o p - u p m o d e is e n t e r e d [7, 8]. Dur-
19
ing 9 h o u r s of t o p - u p o p e r a t i o n t h e S O F B stabilizes
t h e orbit t o R M S v a l u e s of « 1
with r e s p e c t t o t h e
" G o l d e n Orbit" in b o t h p l a n e s . T h e R F f r e q u e n c y is corrected by df w h e n e v e r |df | e x c e e d s 5 H z c o r r e s p o n d i n g
t o d P / P w 2 e - 5 . In this particular c a s e a f r e q u e n c y correction is p e r f o r m e d every « 4 5 m i n . P l e a s e note that
t h e horizontal R M S v a l u e i n c r e a s e s ( s e e " s a w t o o t h "
in F i g . 2) w h i l e df is n o t a p p l i e d . F i g . 3 s h o w s t h e
320 mA top-up
dP/P - 2 e - 5
¡
NrSNIs
urn
laps
IAHIDI-BPM:OFB-XHMS
( - Z 1 . 2 9 ) VAL=1.016Z1
x R M S D f difference orliit
lARIDI-BPMiÖFB-VRMS
" ( 0 , 5 0 ) V A I 0.r.79G!)»
y R M S of difference orbit
ARIDI-BPM:ÖFB-DF
( 1 8 0 . ? 0 ) VAI-Il
proposed frequency change
< «ARIDI-BPM:OFB-XMEAN
(-35, 15) VAL—0.120508
x mean difference orbit
!SARIDI-BPM:OFB-YMEAN
(-14, 36) VAL—0.0100528
y mean difference orbit
j
[5] A . L ü d e k e , M. B ö g e , J . C h r i n , High Level
Software
and Operator Interface, P S I Scientific R e p o r t 2 0 0 1 ,
VII.
[6] M. B ö g e , J . C h r i n , On the Use of CORBA in High
Level Beam Dynamics Applications
at the SLS, P S I
Scientific R e p o r t 2 0 0 1 , V I I .
[7] A . S t r e u n et al., Achievements
of the SLS Commissioning, P S I Scientific R e p o r t 2 0 0 1 , V I I .
[8] M. M u ñ o z , Top-up Operation,
2001, VII.
P S I Scientific R e p o r t
ARÍDI-BPM-05SB •> U24
y reí position •
a)
x RMS orbit
E 824
x=(-21:29|um
y RMS orbit
y=[0:50| um
'06:39:34, 5.5252)
4-
•» M O *
(Hours)
*
I
9
j
H +
x position [urn]
F i g . 2 : S c r e e n s h o t depicting R M S v a l u e s of t h e horizontal ("x R M S " ) a n d vertical ("y R M S " ) deviations f r o m
t h e " G o l d e n Orbit" of « 1 f i m d u r i n g a 9 hour " t o p - u p "
run at 3 2 0 m A . T h e p r o p o s e d f r e q u e n c y c o r r e c t i o n df is
a p p l i e d w h e n p a s s i n g a t h r e s h o l d of 5 H z c o r r e s p o n d ing t o a n e n e r g y deviation d P / P « 2 e - 5 .
variation of t h e orbit position at t h e location of ID U 2 4
over 13 h o u r s of t o p - u p o p e r a t i o n . T h e v a l u e s a r e e x t r a p o l a t e d f r o m t h e r e a d i n g s of t h e a d j a c e n t B P M u p s t r e a m . T h e d e v i a t i o n s f r o m t h e " G o l d e n Orbit" a r e well
fitted by G a u s s i a n distributions with 2 n d m o m e n t s of
a = 0.5 fim a n d a = 0.7 fim, respectively.
x
y
2500
2000
1500
1000
500
x position [urn]
5000
ARIDI-BPM-Q5SB -> U24 -
,.Mikc¿~u£a.i>ml.:
C)
3500
3000
2500
2000
1500
1000
REFERENCES
500
[1] V. Schlott et al., Digital BPM System - Proof of Functionality, P S I Scientific R e p o r t 2 0 0 0 , V I I .
[2] F. J e n n i , H. Horvat, L. Tanner, Precision
Power Supplies,
3500
3000
4000
S h o r t a n d long t e r m orbit stabilities of < 1 ¿¿m at t h e location of t h e IDs a n d a n e n e r g y stability of d P / P « 2 e - 5
h a v e b e e n a c h i e v e d . T h e s u c c e s s f u l c o m m i s s i o n i n g of
t h e S O F B is a n i m p o r t a n t s t e p t o w a r d s t h e i m p l e m e n tation of t h e F O F B .
ílüí<xS=a.5.2.um)...:
4000
4500
OUTLOOK
ARIDI-BPM-Q5SB -> U24 •
4500
of the SLS
P S I Scientific R e p o r t 2 0 0 0 , V I I .
[3] M. B ö g e , Transverse Stabilization
PSI Scientific R e p o r t 1998, V I I .
of the SLS Beam,
[4] S. Hunt et al., Status of the SLS Control
PSI Scientific R e p o r t 2 0 0 1 , V I I .
System,
0
820
822
824
y position [urn]
F i g . 3: S c a t t e r p l o t a) of t h e p r o j e c t e d orbit position
at t h e location of ID U 2 4 t a k e n at a s a m p l i n g rate of
1 H z over a 13 hour t o p - u p r u n a n d c o r r e s p o n d i n g hist o g r a m s for t h e horizontal b) a n d vertical c) b e a m m o tion. T h e 2 n d m o m e n t s of t h e G a u s s i a n distributions
a r e fitted t o b e a = 0.5 ¿¿m a n d a = 0 . 7 ¿¿m, r e s p e c tively.
x
y
20
OPERATION OF THE SLS STORAGE RING RF SYSTEM
P. Marchand,
M. Pedrozzi,
d. Cherix,
C. Geiselhart,
W. Portmann,
W. Tron
The RF system of the SLS storage ring consists of four 500 MHz power plants. The installation
of the last
plant was completed
in the eady 2001. Improved
versions of phase, amplitude
and tuning loops
have
been implemented
as well as additional
filtering in the klystron HV power supplies. Presently, the four
plants can operate up to 320 mA of stored beam, without excitation of cavity Higher Order Modes
(HOM).
The design current of 400 mA was reached in spite of the weak excitation of one longitudinal
HOM.
INTRODUCTION
T h e R F s y s t e m of t h e S L S s t o r a g e ring c o m p r i s e s
four 5 0 0 M H z p o w e r plants, w h i c h c a n g e n e r a t e a
total R F v o l t a g e of 2.4 M V a n d deliver 2 4 0 k W into t h e
b e a m [1]. E a c h plant c o n s i s t s m a i n l y of a single cell
c o p p e r c a v i t y of t h e E L E T T R A t y p e p o w e r e d w i t h a
180 k W klystron amplifier.
T h e m o d u l a r i t y of t h e R F s y s t e m a l l o w e d u s t o operate u p t o m o r e t h a n 3 0 0 m A u s i n g t h r e e plants o u t of
four. T h i s flexibility largely simplified t h e m a i n t e n a n c e
a n d u p g r a d i n g of the s y s t e m d u r i n g t h e o p e r a t i o n . For
i n s t a n c e , t h e b r e a k d o w n of a p o w e r c o u p l e r in S e p tember had minimum impact on the operation, which
c o u l d restart after a relatively short intervention; t h e
c o u p l e r w a s r e p l a c e d d u r i n g t h e next s c h e d u l e d shutd o w n . T h e failure w a s d u e t o a r c i n g o n t h e c e r a m i c
w i n d o w , p r o b a b l y c a u s e d b y a small metallic c h i p
introduced during the mounting.
O n e p a s s i v e c a v i t y w a s a l s o t e m p o r a r i l y u s e d a s "a
d i a g n o s t i c tool" f o r m e a s u r e m e n t s of t h e s y n c h r o n o u s
phase a n d synchrotron frequency.
Upgrading
Electronic'racks
Klystron
c
°°
l i n
9
r a c k
F i g . 1 : S t o r a g e ring R F plants 1 a n d 2.
The RF voltage amplitude, phase a n d the frequency
t u n i n g of t h e c a v i t y a r e r e g u l a t e d b y m e a n s of t h r e e
control loops. T h e t u n i n g loop k e e p s c o n s t a n t t h e
fundamental mode frequency by mechanical change
of t h e c a v i t y l e n g t h . In o r d e r t o c o p e with t h e Higher
O r d e r M o d e s ( H O M ) , that c o u l d drive c o u p l e d b u n c h
instabilities, t w o a d d i t i o n a l t u n i n g m e a n s a r e u s e d : a
fine control of t h e c a v i t y t e m p e r a t u r e a n d a plunger.
Insertion of filters at t h e o u t p u t of t h e klystron H V
s w i t c h e d p o w e r s u p p l i e s significantly r e d u c e d t h e
v o l t a g e ripple g e n e r a t e d at high f r e q u e n c y , e s p e c i a l l y
in t h e critical r a n g e of 4 - 12 k H z . T a b l e 2 s h o w s t h e
ripple spectral c o m p o n e n t s after filtering; t h e overall
v a l u e is less t h a n 0.6 % .
p p
KlystronVoltage
Klystron
Current
[1-2]
kHz
38 kV
5.3 A
6V
45.7 kV
5.3 A
5 Vrms
m s
[2-4]
kHz
[4-12]
kHz
> 12
kHz
4.5 Vrms
3.5 Vrms
23 Vrms
3.5 Vrms
10 Vrms
5V
m s
OPERATION RESULTS
T a b l e 2 : Ripple of t h e H V s w i t c h e d p o w e r s u p p l i e s .
General
T h e phase a n d amplitude loops were also modified for
i n c r e a s i n g their b a n d w i d t h u p t o 4 k H z . T h e residual
R F p h a s e noise, m e a s u r e d after t h e s e i m p r o v e m e n t s ,
w a s less t h a n 0 . 5 ° in t h e f r e q u e n c y r a n g e 0 - 4 0 k H z .
E n d of J a n u a r y 2 0 0 1 , t h e fourth s t o r a g e ring plant w a s
c o m m i s s i o n e d a n d t h e four cavities w e r e s i m u l t a n e o u s l y p o w e r e d f o r o p e r a t i o n with b e a m . All plants
h a v e r u n f o r m o r e t h a n 3 0 0 0 h o u r s with a l o w failure
rate. T y p i c a l c a v i t y w o r k i n g c o n d i t i o n s f o r a stored
b e a m of 2 0 0 m A a r e s h o w n in T a b l e 1 .
Nb. of
active
cavities
Gap
voltage
[kV]
Incident
power
[kW]
Reflected
power
[kW]
Vacuum
level
[mbar]
4
550
71
1
5.10"
9
3
650
105
2
6.10"
9
In 2 0 0 2 , t h e m a i n s t o r a g e ring 5 0 0 M H z s y s t e m will b e
c o m p l e m e n t e d with a third h a r m o n i c idle s u p e r - c o n d u c t i n g cavity, w h i c h will l e n g t h e n t h e b u n c h e s a n d
c o n s e q u e n t l y i m p r o v e t h e b e a m lifetime [2].
HIGHER ORDER MODE TUNING
T h e interaction of t h e b e a m with a c a v i t y H O M i m p e d a n c e c a n lead t o C o u p l e d B u n c h Instabilities ( C B I ) .
T h e C B I g r o w t h rate, G d e p e n d s o n t h e f r e q u e n c y
detuning between the H O M resonance a n d the coupled b u n c h m o d e f r e q u e n c i e s :
m
T a b l e 1 : C a v i t y w o r k i n g c o n d i t i o n s with 2 0 0 m A .
It is w o r t h w h i l e t o note that a t t h e b e g i n n i n g of t h e
s t o r a g e ring c o m m i s s i o n i n g t h e c a v i t y
vacuum
r e a c h e d a b o u t 1.10 " m b a r with o n l y a f e w m A of
s t o r e d b e a m a n d this v a c u u m p r e s s u r e c o n t i n u o u s l y
improved during the operation.
7
p p
I R
1 + 2ô
m
21
I is t h e s t o r e d b e a m current, R , Q a n d v are res p e c t i v e l y t h e H O M s h u n t i m p e d a n c e , quality factor
a n d f r e q u e n c y ; v (p = 1,2,...°°) are t h e c o u p l e d b u n c h
mode frequencies:
b
sn
m
n
p
\v
longitudinal c a s e
s
P-v ±i
:
rw
situation c o u l d certainly be i m p r o v e d , u s i n g t h e
p l u n g e r a s third d e g r e e of f r e e d o m for t u n i n g t h e
H O M ; this r e q u i r e s f u r t h e r i n v e s t i g a t i o n s with d e d i c a t e d b e a m t i m e . M o r e o v e r , t r a n s v e r s e a n d longitudinal f e e d b a c k s will be s o o n i m p l e m e n t e d that will c o n tribute t o d a m p the C B I .
transverse case
V,
Cav4 - 400 mA - Plunger fully out
w h e r e v , Vß a n d v are t h e s y n c h r o t r o n , b e t a t r o n a n d
revolution f r e q u e n c i e s , respectively.
rev
s
T h e stability is e n s u r e d if t h e C B I g r o w t h rate is l o w e r
t h a n t h e natural radiation d a m p i n g rate.
F o l l o w i n g t h e t e c h n i q u e d e v e l o p e d at E L E T T R A [3],
the H O M t u n i n g is c o n t r o l l e d via t h e cavity t e m p e r a ture, w h i c h c a n be s e t b e t w e e n 3 6 ° C a n d 7 0 ° C w i t h
a c c u r a c y better t h a n ± 0.1 ° C . For a n y c h a n g e of t e m p e r a t u r e , the t u n i n g loop k e e p s c o n s t a n t the f u n d a m e n t a l f r e q u e n c y by m e c h a n i c a l d e f o r m a t i o n of the
cavity. T h e effective H O M f r e q u e n c y shift per d e g r e e
is t h u s :
36
38
40
42
46
50
52
54
56
58
60
62
64
Temperature (°C)
F i g . 2 : Cavity 4 H O M t e m p e r a t u r e m a p .
L
dT
a
m
= Sv
dT
Jeff
CAV 3 • 400 mA - plunger fully out
T = Sv /b~T ( o p e n loop) a n d v is t h e
/Sv ,
m
m0
0
0
0
0
fundamental m o d e frequency.
T h e H O M p a r a m e t e r s of e a c h cavity w e r e m e a s u r e d
at low p o w e r a n d u s e d t o calculate their f r e q u e n c y
v e r s u s t e m p e r a t u r e ; a s a n e x a m p l e , the longitudinal
m o d e p a r a m e t e r s of cavity 4 are listed in T a b l e 3.
Mode
v (40 C)
MHz
L0
499.822
1
-9.4
86
13578
1168.
L1
948.046
0.62
-10.4
29
26453
767.1
L2
1058.485
-0.3
-19.2
0.9
6048
5.4
L3
1420.62
-2.29
-43.7
5.0
30224
151.1
L4
1514.216
-0.5
-32.2
4.3
4400
18.9
CONCLUSIONS
L5
1606.873
-3.83
-57.2
8.9
40888
363.9
L6
1874.467
-0.404
-33.6
0.4
37328
14.9
L7
1947.189
-2.3
-52.4
1.9
16884
32.1
L8
2071.967
-8.
-100.0
0.1
15000
1.5
L9
2123.04
-8.47
-107
7.9
29763
235.1
T h e S L S R F s y s t e m h a s p r o v e n to be quite reliable
during its first y e a r of o p e r a t i o n . T h e m a j o r t r o u b l e
c a m e f r o m the b r e a k d o w n of a cavity p o w e r coupler,
p r o b a b l y d u e t o a b a d m o u n t i n g . Presently, 3 2 0 m A
c a n be s t o r e d w i t h o u t H O M e x c i t a t i o n ; t h e d e s i g n
c u r r e n t of 4 0 0 m A w a s r e a c h e d w i t h a w e a k excitation
of o n e longitudinal H O M . T h e s u p p r e s s i o n of the rem a i n i n g H O M e x c i t a t i o n at full b e a m c u r r e n t requires
further o p t i m i s a t i o n of cavities 2 a n d 3.
m
R/Q
o
OCm
kHzTC
ii
Q
Rsm
m
ka
36
T a b l e 3: C a v i t y 4 longitudinal m o d e p a r a m e t e r s .
F r o m the c a l c u l a t e d H O M f r e q u e n c i e s w e c o u l d t h e n
c o m p u t e t h e C B I g r o w t h rates a n d p r o d u c e t e m p e r a ture m a p s as s h o w n in Fig. 2 a n d 3, for e a c h cavity.
A s a n e x a m p l e , the g r a p h in Fig. 2 s h o w s a large s t a ble t e m p e r a t u r e w i n d o w (53 - 5 9 ° C ) for cavity 4 a n d
that w a s e x p e r i m e n t a l l y c o n f i r m e d in o p e r a t i o n w i t h
b e a m . In t h e s a m e w a y , a stable w o r k i n g point w a s
easily f o u n d for cavity 1 . O n t h e o t h e r h a n d , o n l y v e r y
n a r r o w stable w i n d o w s w e r e f o u n d for cavity 2 a n d 3
(Fig. 3) a n d that resulted in a w e a k excitation of a
longitudinal H O M a b o v e 3 2 0 m A of s t o r e d b e a m . T h e
38
40
42
50
52
54
56
58
60
62
64
Temperature (°C)
F i g . 3: Cavity 3 H O M t e m p e r a t u r e m a p .
REFERENCES
[1]
P. M a r c h a n d et al, P A C 9 9 , p. 9 8 6 .
[2]
P. M a r c h a n d
et
al,
SZ.S
Third
Superconducting
RF
System,
PSI
Reprot 2 0 0 1 , V o l u m e VII.
[3]
M. S v a n d r l i k et al, E P A C 9 6 , p. 1 1 4 4 .
harmonic
Scientific
22
RESULTS OF SURVEY AND ALIGNMENT
F.Q. Wei,
K. Dreyer,
OVERVIEW
T h e S w i s s Light S o u r c e ( S L S ) , a third g e n e r a t i o n light
s o u r c e , is a high-brilliance m a c h i n e d e s i g n e d for ext r e m e l y low e m i t t a n c e , a n d is, t h e r e f o r e , highly s e n s i tive to a l i g n m e n t errors. T h e S L S c o n s i s t s of linac,
booster, s t o r a g e ring, t r a n s f e r lines a n d b e a m lines.
T h e i r n e t w o r k a n d s e v e r a l h u n d r e d s of m a g n e t s a n d
other c o m p o n e n t s of m a c h i n e a n d t h e b e a m lines
w e r e m e a s u r e d a n d a l i g n e d in t h e last 3 y e a r s m a i n l y
by u s i n g t h e laser t r a c k e r L T D 5 0 0 a n d o t h e r s u r v e y
i n s t r u m e n t s . A relative a c c u r a c y of o n e t e n t h of millim e t e r h a s b e e n a c h i e v e d for m o s t m a g n e t s a n d s o m e
other c o m p o n e n t s .
In t h e first a t t e m p t , t h e injected b e a m p a s s e d t h r o u g h
both, t h e b o o s t e r in J u l y 2 0 0 0 a n d t h e s t o r a g e ring in
D e c e m b e r 2 0 0 0 w i t h all c o r r e c t o r s s w i t c h e d off. O n
the third d a y of t h e s t o r a g e ring c o m m i s s i o n i n g a
2 m A e l e c t r o n b e a m w a s s t o r e d w i t h a lifetime of
8 h o u r s . In A u g u s t 2 0 0 1 , t h e S L S w e n t into o p e r a t i o n
t h r e e y e a r s after g r o u n d b r e a k i n g of t h e S L S b u i l d i n g .
T h e p h o t o n b e a m s of t h e four initial b e a m lines h a v e
b e e n a l i g n e d to their e n d stations.
H.
Umbricht
network was measured again with the LTD500. The
s t a n d a r d d e v i a t i o n of t h e s e c o n d m e a s u r e m e n t s w a s
0 . 0 7 9 m m . T h e t u n n e l n e t w o r k w a s m e a s u r e d in
J a n u a r y 2 0 0 0 for t h e 3rd t i m e . A t this t i m e t h e s h i e l d ing wall of the t u n n e l w a s c o m p l e t e d . All wall references were fixed. Therefore, the environmental condit i o n s w e r e better. T h e s t a n d a r d d e v i a t i o n of t h e 3rd
m e a s u r e m e n t s w a s 0 . 0 7 3 m m . In A u g u s t of 2 0 0 0 a n d
J a n u a r y of 2 0 0 1 the t u n n e l a l i g n m e n t n e t w o r k w a s
m e a s u r e d before a n d after the final a l i g n m e n t of the
s t o r a g e ring. T h e s t a n d a r d deviation of t h e last t w o
t u n n e l n e t w o r k m e a s u r e m e n t s w a s 0.066 m m . A better result of t h e a l i g n m e n t n e t w o r k w a s r e a c h e d bec a u s e t h e e n v i r o n m e n t a l c o n d i t i o n s b e c a m e better
a n d our m e a s u r e m e n t t e a m b e c a m e m o r e e x p e r i enced.
DS
F i g . 2 D e f o r m a t i o n s of t h e t u n n e l n e t w o r k f r o m July
1999 to January 2 0 0 1 .
EXPERIMENTAL NETWORK
F i g . 1 : A l i g n m e n t T e a m in a h u t c h of the
Crystallography Beamline.
Protein
TUNNEL NETWORK
Up to n o w , t h e t u n n e l n e t w o r k h a s b e e n m e a s u r e d 5
t i m e s for the first t i m e in M a y 1 9 9 8 . A precision level
N 3 i n s t r u m e n t w a s u s e d t o m e a s u r e t h e e l e v a t i o n s of
the t u n n e l n e t w o r k . At the s a m e t i m e , t h e n e t w o r k w a s
m e a s u r e d w i t h the L T D 5 0 0 u s i n g s o f t w a r e A x y z . T h e
m e a s u r e m e n t s w e r e p e r f o r m e d in 5 3 stations n e a r b y
e a c h floor r e f e r e n c e . A t least t w o floor r e f e r e n c e s a n d
t w o wall r e f e r e n c e s of e a c h side, f o r w a r d a n d backw a r d w e r e m e a s u r e d at e a c h s t a t i o n . At that t i m e , the
s h i e l d i n g w a l l w a s not c o m p l e t e d . Civil e n g i n e e r i n g
w o r k w a s g o i n g on n e a r b y a n d 12 wall r e f e r e n c e s
w e r e m i s s i n g . B e c a u s e of the poor e n v i r o n m e n t a l
c o n d i t i o n s the s t a n d a r d d e v i a t i o n ( 1 a ) of t h e first
m e a s u r e m e n t s w a s 0 . 0 9 3 m m . In J u l y 1 9 9 9 t h e t u n n e l
T h e e x p e r i m e n t n e t w o r k m e a s u r e d for t h e first t i m e in
July 1 9 9 9 by u s i n g T h e o d o l i t e T D A 5 0 0 5 . T h e e x p e r i m e n t a r e a w a s free for s u r v e y at that t i m e . T h e s t a n d a r d d e v i a t i o n (1 a ) of the m e a s u r e m e n t s w a s
0.352 m m . T h e e x p e r i m e n t n e t w o r k w a s m e a s u r e d
S e p t e m b e r 2 0 0 1 by T h e o d o l i t e T D A 5 0 0 5 a n d L a s e r
t r a c k e r L T D 5 0 0 . S e v e r a l a r e a s of the e x p e r i m e n t a l
hall w e r e c o v e r e d . M a n y a d d i t i o n a l r e f e r e n c e s w a r e
a d d e d inside of t h e b e a m line h u t c h e s . S o m e t e m p o rary r e f e r e n c e s h a d t o be a d d e d . T h e s t a n d a r d d e v i a tion of t h e m e a s u r e m e n t s w a s 0 . 3 5 4 m m at this t i m e .
T h e m a x i m u m d e v i a t i o n of t h e e x p e r i m e n t n e t w o r k
f r o m J u l y 1 9 9 9 to S e p t e m b e r 2 0 0 1 is a b o u t 2 m m .
S T O R A G E RING
T h e S L S s t o r a g e ring c o n s i s t s of 4 8 girders. All t h e
q u a d r u p o l e s , s e x t u p o l e s a n d B P M s are well f i x e d o n
t h e g i r d e r s u s i n g f o r c e d c e n t e r m o u n t i n g s y s t e m s . In
o r d e r t o c h e c k t h e p o s i t i o n s of the m a g n e t s on g i r d e r s
in r e s p e c t t o t h e p o s i t i o n s of 4 girder r e f e r e n c e s , all
m e c h a n i c a l c e n t e r s of the q u a d r u p o l e s a n d s e x t u p o l e s of the s t o r a g e ring w e r e m e a s u r e d by t h e laser
t r a c k e r L T D 5 0 0 . A s t a n d a r d d e v i a t i o n of t h e p o s i t i o n s
of m e c h a n i c a l c e n t e r s of t h e m a g n e t s in r e s p e c t t o
positions of t h e girder r e f e r e n c e s w a s 0.044 m m a n d
0.030 m m in t h e radial direction a n d in t h e vertical
direction respectively.
23
Each quadrupole and sextupole has two reference
h o l e s on t h e t o p r e f e r e n c e s u r f a c e . Positions of t h e
r e f e r e n c e s of all c o m p o n e n t s o n a girder with r e s p e c t
to t h e t u n n e l n e t w o r k w e r e m e a s u r e d by t h e laser
t r a c k e r L T D 5 0 0 . T h e g e n e r a l d e v i a t i o n s of t h e girder
position in r e s p e c t t o its ideal positions w e r e c a l c u lated by a n IDL p r o g r a m . T h e girder w a s a d j u s t e d by
the m o v e r s y s t e m . A s t a n d a r d d e v i a t i o n of 0.1 m m
( 1 a ) of the r e f e r e n c e p o s i t i o n s w a s r e a c h e d after 2 or
3 iterations of the a b o v e m e a s u r e m e n t a n d adjustm e n t . A s t a n d a r d d e v i a t i o n of the r e f e r e n c e positions
on all 4 8 g i r d e r s w i t h r e s p e c t t o t h e ideal positions
w a s 0.085 m m a n d 0.040 m m in t h e radial direction
a n d in t h e vertical direction respectively.
M o s t c o m p o n e n t s of t h e b e a m lines h a v e s e v e r a l
r e f e r e n c e holes. T h e y c a n be u s e d for positioning t h e
c o m p o n e n t s w i t h r e s p e c t t o t h e s t o r a g e ring position.
T h e final a l i g n m e n t will b e realised by t h e s y n c h r o t r o n
radiation b e a m itself.
SLS survey and alignment group supported the b e a m
lines o n t h e f o l l o w i n g t a s k s :
F i g . 3: D e v i a t i o n s of the r e f e r e n c e positions o n 4 8
girders of the s t o r a g e ring w i t h r e s p e c t t o t h e ideal
positions.
•
providing a g e n e r a l a l i g n m e n t n e t w o r k in t h e
e x p e r i m e n t a l hall,
•
a d d i n g a d d i t i o n a l local a l i g n m e n t
during t h e c o n s t r u c t i o n p h a s e ,
•
supplying the general information about c o m ponent references and adjusting systems,
•
m a r k i n g the positions of b e a m axis a n d s u p port feet o n t h e floor,
•
pre-aligning a n d calibrating c o m p o n e n t s
fore installation,
•
aligning c o m p o n e n t s d u r i n g installation,
•
a d j u s t i n g c o m p o n e n t s during t h e c o m m i s s i o n ing of the b e a m lines.
networks
be-
A L I G N M E N T OF LINAC, T R A N S F E R LINE A N D
BOOSTER
T h e r e are at least 3 r e f e r e n c e h o l e s o n t h e top of
e a c h c o m p o n e n t of the Linac, t h e transfer line, a n d
the booster. All the c o m p o n e n t s w e r e f i x e d o n their
s u p p o r t s individually. T h e s a m e a l i g n m e n t instrum e n t a t i o n L T D 5 0 0 is u s e d to m e a s u r e the positions of
the c o m p o n e n t r e f e r e n c e s a n d to adjust directly into
their ideal positions. S t a n d a r d d e v i a t i o n s of t h e positions of all t h e b o o s t e r r e f e r e n c e s w i t h r e s p e c t to t h e
ideal positions w e r e 0 . 0 5 7 m m a n d 0.045 m m in t h e
radial direction a n d in t h e vertical direction r e s p e c tively.
F i g . 4 : D e v i a t i o n s of t h e positions of all t h e b o o s t e r
c o m p o n e n t r e f e r e n c e s in r e s p e c t to t h e ideal positions.
ALIGNMENT OF THE B E A M LINES
T h e f o u r existing b e a m lines, the M a t e r i a l s S c i e n c e
B e a m l i n e , t h e Protein C r y s t a l l o g r a p h y B e a m l i n e , t h e
Surfaces/interfaces Spectroscopy Beamline, and the
S u r f a c e s / I n t e r f a c e s M i c r o s c o p y B e a m l i n e , c o n s i s t of
insertion d e v i c e s , f r o n t e n d s , m o n o c h r o m a t o r s , mirror
b o x e s , slits, a n d e x p e r i m e n t a l stations.
F i g . 5: P r e - a l i g n m e n t of Insertion D e v i c e 9 L .
F i g . 6: T h e vertical pole d e v i a t i o n s of the
device 9L.
insertion
T h e S L S survey and alignment group has successfully
p o s i t i o n e d all c o m p o n e n t s of t h e four b e a m lines w i t h
high a c c u r a c y . T h e p h o t o n b e a m s w e r e g u i d e d
t h r o u g h t h e optics until t o t h e e n d stations w i t h i n short
t i m e for all b e a m l i n e s currently in o p e r a t i o n .
REFERENCES
[1]
F . Q . W e i et al, Survey
and Alignment
for the
Swiss Light Source, 6
International W o r k s h o p
on Accelerator Alignment, Grenoble, October,
1999.
t h
24
SLS OPERATION
A.
Lüdeke
August
2001 saw the official start of user operation
at the SLS. Already
before that date, pilot
users
started taking data at the first beamlines.
With the transition from SLS commissioning
to user
operation,
the demands on the machine operation shifted from maximum flexibility to optimal
reliability.
INTRODUCTION
USER OPERATION REQUIREMENTS
T h e transition f r o m c o m m i s s i o n i n g t o user o p e r a t i o n
of t h e S L S started a l r e a d y in M a y 2 0 0 1 with the first
o p e r a t i o n of t h e protein c r y s t a l l o g r a p h y b e a m l i n e [1].
Since then, more and more beam-time was dedicated
to user o p e r a t i o n , as s h o w n in Fig. 1.
T h e default o p e r a t i o n m o d e for s y n c h r o t r o n light users
is t h e t o p - u p m o d e . In this m o d e , the u n a v o i d a b l e
l o s s e s of t h e e l e c t r o n b e a m in t h e s t o r a g e ring are
c o m p e n s a t e d by re-injecting in s h o r t t i m e intervals of
2 0 to 120 s e c o n d s , to k e e p t h e b e a m c u r r e n t stable
w i t h i n less t h a n 1 %. N o r m a l o p e r a t i o n w o u l d n e e d
refilling j u s t a f e w t i m e s per day. T h e t o p - u p m o d e
p r o v i d e s e x c e l l e n t stability for the s t o r a g e ring a n d t h e
b e a m l i n e s , s i n c e all t y p e s of drifts d u e to v a r i a b l e
t h e r m a l loads are m i n i m i z e d . O n t h e other h a n d , it
requires t o o p e r a t e t h e injector c o n t i n u o u s l y . T h e r e fore, the stability of t h e injector s y s t e m h a s t o be
m u c h higher t h a n for o t h e r light s o u r c e s . T o i m p r o v e
this stability will be crucial for user o p e r a t i o n in 2 0 0 2 .
60
r—.
T
5 0 --
o
-
o
J
o
U
-
o
2
o
<
o
2
-
o
,
o
^
o
<
C
o
O
T
o
O
o
Z
o
Q
.
• Machine Shifts • U s e r Shifts
F i g . 1 : M o n t h l y shift a l l o c a t i o n for t h e S L S
In 2 0 0 2 , t h e total n u m b e r of shifts per m o n t h will inc r e a s e steadily. T a r g e t e d for the first half of 2 0 0 2 is
an a v e r a g e of 5 9 shifts per m o n t h , w h e r e 4 7 shifts or
8 0 % will be d e d i c a t e d t o o p e r a t i o n for u s e r s . T h e m a c h i n e shifts will be u s e d to c h a r a c t e r i z e a n d o p t i m i z e
the m a c h i n e a n d t o integrate n e w insertion d e v i c e s .
ORGANIZATION OF THE OPERATION
U s e r o p e r a t i o n is a l r e a d y fully a u t o m a t e d a n d d o e s
not n e e d intervention by an operator. Still t w o
o p e r a t o r s n e e d t o be p r e s e n t for safety r e a s o n s ,
t r o u b l e s h o o t i n g , a n d for the control of insertion
d e v i c e s o n d e m a n d of the u s e r s . T h e n u m b e r of
p e r s o n s for m a c h i n e o p e r a t i o n d e p e n d s o n t h e
p r o g r a m a n d varies b e t w e e n t w o a n d f o u r p e o p l e .
For the c o m m i s s i o n i n g a p p r o x . 30 p e o p l e f r o m the
m a c h i n e c r e w participated in t h e o p e r a t i o n for up t o
2 0 % of their t i m e . S i n c e last O c t o b e r the training of
full t i m e o p e r a t o r s s t a r t e d . F r o m n o w o n , t h e shifts will
be m a n n e d by o n e o p e r a t o r a n d o n e m e m b e r of t h e
m a c h i n e staff. T h i s allows for c o v e r i n g t h e a d d i t i o n a l
shifts a n d s u p p o r t i n g t h e training of t h e full t i m e o p erators.
T h e reliability of m a c h i n e o p e r a t i o n is d e t e r m i n e d by
t h e reliability of all s u b s y s t e m s a n d by t h e p r o c e d u r e s
t o e s t a b l i s h a certain o p e r a t i o n m o d e .
M o d i f i c a t i o n s of a n y s u b s y s t e m c a n require adjustm e n t s t o the s e t - u p s for an o p e r a t i o n m o d e a n d a l s o
t o t h e p r o c e d u r e s to re-establish a s e t - u p . D u r i n g t h e
commissioning these changes occurred frequently,
d u e t o t h e o n g o i n g e n h a n c e m e n t s of m a n y s u b s y s t e m s . H o w e v e r , for the user o p e r a t i o n stable a n d relia b l e s e t - u p p r o c e d u r e s are r e q u i r e d to e n s u r e t h e
r e p r o d u c t i o n of all m a c h i n e p a r a m e t e r s . T h e r e f o r e it is
crucial to q u i c k l y c o m m u n i c a t e a n y m o d i f i c a t i o n , in
o r d e r t o p r e p a r e test p r o c e d u r e s for d e p e n d e n t s u b s y s t e m s . W e will u s e the O r a c l e d a t a b a s e t o collect all
m o d i f i c a t i o n s a n d to a u t o m a t i c a l l y c o m m u n i c a t e t h e m
t o t h e relevant p e o p l e .
SUMMARY
T h e S L S is currently in t h e transition f r o m c o m m i s s i o n i n g to user o p e r a t i o n . T h e flexibility, that w a s
n e e d e d for the rapid build up of t h e m a c h i n e , m u s t
n o w be t r a d e d with the reliability that is r e q u i r e d t o
o p e r a t e it as a user facility. T h e training of full t i m e
o p e r a t o r s a n d o b l i g a t o r y p r o c e d u r e s for m o d i f i c a t i o n s
will help us t o e n s u r e reliable o p e r a t i o n s .
REFERENCES
[1]
A. S t r e u n , Commissioning
of the Swiss
Source, h t t p : / / s l s b d . p s i . c h / p u b / c o m m /
[2]
M. M u ñ o z , Top-up operation,
port 2 0 0 1 , V o l u m e V I I .
Light
PSI Scientific R e -
25
OPERATING EXPERIENCE WITH THE SLS POWER SUPPLIES
F. Jenni,
By the end of
at 7 A/ 24 V
look identical,
pleasing.
The
countered.
M. Horvat,
L.
Tanner
2001, the SLS is using more than 580 digitally controlled power supplies. Their ratings
start
for the smallest and go up to 950 A / 1000 V for the largest. For the operators,
all of them
independent
of their ratings. The experience
of more than one year of operation
is very
chosen concept proved to meet the specifications.
Only few hardware
failures were en-
INTRODUCTION
T h e S L S is t h e first a c c e l e r a t o r w h e r e all t h e m a g n e t
p o w e r s u p p l i e s ( P S ) a r e c o n t r o l l e d digitally. C o n t r o l
principle a n d h a r d w a r e h a v e b e e n d e v e l o p e d a n d built
f r o m s c r a t c h , i.e. t h e r e w a s no p r e v i o u s e x p e r i e n c e
with s u c h a s t r u c t u r e at P S I . F u r t h e r m o r e , t h e w h o l e
d e v e l o p m e n t a n d p r o d u c t i o n h a d to b e d o n e w i t h i n a
v e r y short t i m e s p a n . All t h e p o w e r electronic h a r d w a r e w a s d e s i g n e d by P S I . T h e controller h a r d w a r e
a n d t h e high precision A D - c o n v e r t e r w h e r e s p e c i f i e d
by PSI in detail. T w o e x t e r n a l c o m p a n i e s m a d e t h e
final d e s i g n . All P S w e n t into o p e r a t i o n o n t i m e .
v o l t a g e s t e p s (20 u V = 2 p p m ) at t h e input. T h e t o p
g r a p h s h o w s t h e v a l u e s of 50 s a m p l e s per s e c o n d
(sps). E a c h of t h e s a m p l e s is t h e a v e r a g e v a l u e of
4 0 0 0 d a t a points ( o v e r s a m p l i n g ) . T h e b o t t o m g r a p h is
m a d e of 5 0 0 s p s c o r r e s p o n d i n g t o a n a v e r a g e of 4 0 0
data points. W i t h t h e d e v e l o p e d digital control unit a
resolution t o 1 p p m is possible.
ADC Resolution: @ 50 samples/s (1V offset, 2ppm (20uV) steps)
E
9-12
o
E
T h e P S in t h e t r a n s f e r line linac t o b o o s t e r w h e r e
t u r n e d on in s u m m e r 1 9 9 9 , t h o s e in t h e b o o s t e r in
spring 2 0 0 0 a n d t h o s e of t h e s t o r a g e ring in late a u t u m n 2 0 0 0 . In 2 0 0 1 , 8 4 additional units for insertion
d e v i c e s w e r e i m p l e m e n t e d . T h i s leads t o 18 m o n t h s
of e x p e r i e n c e with t h e first b a t c h .
mm
t
I
>
2 o
i
60
80
100
120
Time [min]
N o p r o b l e m s w e r e e n c o u n t e r e d with functionality,
d y n a m i c s a n d precision of t h e P S . All t h e d e m a n d s
w h e r e s u r p a s s e d . A c h i e v e d precision a n d stability a r e
c o n v i n c i n g . Further e x t e n s i o n s of t h e functionality a r e
p o s s i b l e by s i m p l e s o f t w a r e d o w n l o a d s . F u r t h e r m o r e ,
no substantial h a r d w a r e p r o b l e m s o c c u r r e d . A s it is
c o m m o n with s u c h a n u m b e r of d e v i c e s , s o m e indiv i d u a l c o m p o n e n t failures h a d to b e f i x e d .
ADC Resolution: @ 500 samples/s (1V offset, 2ppm (20uV) steps)
STATUS
P r e c i s i o n o f t h e PS
T h e c u r r e n t m e a s u r e m e n t is t h e crucial o p e r a t i o n for
t h e precision a n d stability of t h e P S . T h i s t a s k is perf o r m e d with a direct c u r r e n t t r a n s f o r m e r ( D C C T ) foll o w e d by an a n a l o g t o digital c o n v e r t e r ( A D C ) . Both
o p e r a t i o n s a r e s i t u a t e d in t h e f e e d b a c k path of t h e
control loop. D C C T s a r e a v a i l a b l e with a v e r y high
precision,
according
to
individual
requirements.
T h e r e f o r e , t h e A D - c o n v e r s i o n d e t e r m i n e s t h e final
precision of t h e digital c o n t r o l l e d P S . M e a s u r e m e n t s
on a s t a n d a r d A D C - c a r d u n d e r o p e r a t i n g c o n d i t i o n s
s h o w t h e a c h i e v e d results.
R e s o l u t i o n a n d s h o r t - t e r m s t a b i l i t y (< 6 0 s )
T h e current measurements are m a d e m u c h faster
t h a n n e c e s s a r y . T h i s a l l o w s t h e u s e of an o v e r s a m pling t e c h n i q u e : t h e m e a s u r e d v a l u e s a r e filtered
digitally. T h e low pass characteristic of t h e P S perf o r m s an a d d i t i o n a l filtering.
Fig. 1 c o n f i r m s t h e high r e s o l u t i o n of t h e c o n v e r t e r
c a r d . T h e g r a p h s s h o w t h e digital v a l u e for v e r y s m a l l
0
20
40
60
80
100
120
140
160
Time [min]
Fig
1 A D C input signal for 2 p p m input v o l t a g e s t e p s .
Long-term stability
Fig. 2 s h o w s t h e filtered m e a s u r e d v a l u e o v e r 1 0 0 0
h o u r s . T h e l o n g - t e r m stability for t h e first 1 0 0 0 h is
better t h a n 30 p p m .
26
ADC Long term stability: 1000h
ADC Temperature-sensitivity @ 4.5V input voltage
E "
Q.
a.
• g 10
Q.
E
ion
£ 4
"S
(D
Q-20
0
100
200
300
400
500 600
Time [h]
700
800
900 1000
F i g . 2 : L o n g - t e r m m e a s u r e m e n t o v e r 1 0 0 0 h.
T h i s drift c o r r e s p o n d s t o t h e s p e c i f i c a t i o n d a t a o f t h e
o n b o a r d r e f e r e n c e . It c o u l d drastically be r e d u c e d w i t h
a b u r n i n . T h e drift d e c r e a s e s w i t h t i m e after s e v e r a l
h u n d r e d h o u r s . T h i s w a s c o n f i r m e d with a s u b s e q u e n t
m e a s u r e m e n t : in a n o t h e r 1 0 0 0 h t h e drift w a s in a
r a n g e of + 3 p p m . H o w e v e r , this is a l s o w i t h i n t h e drift
r a n g e of t h e u s e d i n s t r u m e n t .
20
25
30
Time [h]
F i g . 4 : T e m p e r a t u r e sensitivity of t h e A D C ( 1 0 ° C t o
5 0 ° C ) . T h e d a s h e d line is t h e a m b i e n t t e m p e r a t u r e .
Hardware
A brief o v e r v i e w o f e n c o u n t e r e d p r o b l e m s is g i v e n
below:
Linearity
Power converter: T h r e e different p o w e r s t a g e s w e r e
burnt. O n l y in o n e c a s e t h e r e a s o n w a s a s c e r t a i n e d : a
loose s c r e w led t o a n electrical arc.
T h e non-linearity of t h e A D C c a u s e s a n a b s o l u t e error, d e p e n d i n g o n t h e input v o l t a g e . W i t h a d e v i a t i o n
b e t w e e n + 9 p p m a n d - 1 4 p p m ( s e e Figure 3) t h e
a n a l o g t o digital c o n v e r s i o n is v e r y g o o d - t h e error is
less t h a n 1/3 L S B of t h e u s e d A D C !
Control hardware:
T w o systematic problems on the
digital signal p r o c e s s o r c a r d h a d t o be m o d i f i e d : a
m i s s i n g i n t e r c o n n e c t i o n o n t h e printed circuit a n d a
s e r i e s of w e a k d c / d c c o n v e r t e r s . B e s i d e that, a p proximately 10 D S P a n d 10 A D C - c a r d s failed.
Auxiliary
electrical system: A b l o c k e d ventilator a n d 3
auxiliary p o w e r s u p p l i e s n e e d t o be r e p l a c e d .
ADC Linearity
Cooling
system: A burst flexible pipe at t h e w a t e r
cooled mains transformer caused a t w o day shut
d o w n o f t h e s t o r a g e ring b e n d P S .
i-^ia.
j
-4
-3
-2
Alarms of the magnet interlock system
o-
Off.*
a
j
-1
0
1
Input Voltage [V]
2
3
4
5
F i g . 3: Linearity of a n a l o g t o digital c o n v e r s i o n o v e r
the full input r a n g e .
Temperature sensitivity
The voltage
temperature
sensitivity in
be r e d u c e d
above 45°C,
r e f e r e n c e u s e d f o r t h e A D C s h a d t o be
stabilized. Thereby, the temperaturethe operation range (20°C to 45°C) could
d o w n t o 0.5 p p m / ° C . ( B e l o w 1 5 ° C a n d
t h e error i n c r e a s e s a s s h o w n in F i g . 4.)
T h e m a g n e t interlock s y s t e m s u p e r v i s e s t h e m a g n e t
coil t e m p e r a t u r e a n d t h e w a t e r f l o w t h r o u g h t h e coils.
In c a s e of a failure t h e p o w e r s u p p l i e s w e r e t u r n e d off.
A n u m b e r o f P S s h u t d o w n s w e r e c a u s e d by m a g n e t
interlocks: s o m e of t h e s e a l a r m s w h e r e justified, o t h e r s w e r e c a u s e d by d y n a m i c p r e s s u r e d r o p s in t h e
w a t e r s y s t e m . W i t h i m p r o v e m e n t s in t h e m a g n e t
cooling system these alarms vanished.
T h e s e interrupts w e r e m i s i n t e r p r e t e d a s P S e r r o r s by
t h e m a c h i n e o p e r a t o r s in t h e early d a y s o f o p e r a t i o n .
Mishandlings
T h e great flexibility of t h e n e w controllers c a u s e d a l s o
s o m e m i s h a n d l i n g s . N o n e of t h e m c a u s e d a n y d a m age to the PS.
27
Accelerator operation
REFERENCES
T h e stable a n d reliable o p e r a t i o n of all m a g n e t P S
w a s a prerequisite for t h e f a s t p r o g r e s s in t h e c o m m i s s i o n i n g of t h e S L S . E v e r y drift in a n y P S w o u l d
directly influence t h e quality of t h e e l e c t r o n b e a m .
S i n c e all o b s e r v e d drifts are well w i t h i n t h e e x p e c t e d
r a n g e , a n y m e d i u m t e r m drift a b o v e t h e s p e c i f i c a t i o n s
of a n y P S of t h e s t o r a g e ring c a n b e e x c l u d e d . T h e
f e a t u r e to r e a d out e n h a n c e d d i a g n o s t i c s s u c h a s the
m a g n e t r e s i s t a n c e is a great help t o s p e e d u p t h e
s e a r c h of error s o u r c e s .
[1]
G. Irminger, M. Horvat, F. J e n n i , H.U. B o k s b e r ger, A 3Hz, 1MW Bending Magnet Power
Supply
for the Swiss Light source (SLS); E P 2 F o r u m 9 8 ;
Electrical P o w e r T e c h n o l o g y in E u r o p e a n P h y s ics R e s e a r c h .
[2]
F. J e n n i , H.U. B o k s b e r g e r , G. Irminger,
DC-Link
Control
for a 1MVA-3Hz
Single Phase
Power
Supply,
IEEE Power Electronics
Specialists
Conference, 1999.
[3]
J . C a r w a r d i n e , F. L e n k s z u s , Trends in the Use of
Digital Technology
for Control and Regulation
of
Power Supplies, International C o n f e r e n c e o n A c celerator a n d L a r g e E x p e r i m e n t a l P h y s i c s C o n trol S y s t e m s , 1999.
[4]
M. E m m e n e g g e r , F. J e n n i , A Fully Digital
PWM
for Highest Precision
Power Supplies,
European
Power Electronics Conference, 2001
[5]
L. T a n n e r , F. J e n n i , Digital
Control
precision
accelerator
power supplies
cle A c c e l e r a t o r C o n f e r e n c e .
CONCLUSION
T h e digital c o n t r o l l e d p o w e r s u p p l i e s in t h e S L S h a v e
p r o v e n their functionality, precision a n d reliability.
T h e y are well a c c e p t e d by the m a n a g e m e n t a n d by
the t e c h n i c a l staff.
for
highest
2 0 0 1 Parti-
28
RESULTS FROM THE HORIZONTAL POSITION MEASUREMENT SYSTEM
V.
Schlott
A measuring
system for monitoring
the horizontal
positions
of the SLS storage ring girders
stalled and commissioned
during the year 2001. Its integration
into the concept of dynamic
described and first results, indicating girder motions, are
presented.
INTRODUCTION
M a n y s t e p s h a v e b e e n u n d e r t a k e n at the S w i s s Light
S o u r c e ( S L S ) t o provide s y n c h r o t r o n radiation of h i g h est quality u n d e r e x t r e m e l y s t a b l e a n d r e p r o d u c i b l e
conditions. Apart from conventional surveying and
fiducialization of individual i t e m s , an innovative a l i g n m e n t a n d stability c o n c e p t h a s b e e n d e v e l o p e d to
m o n i t o r a n d c o r r e c t m e c h a n i c a l m o t i o n s of s t o r a g e
ring c o m p o n e n t s like m a g n e t s u p p o r t s t r u c t u r e s (girders), b e a m position m o n i t o r s ( B P M ) a n d insertion dev i c e s (ID) to a m i c r o m e t e r level. T h e m a i n f e a t u r e s of
this c o n c e p t are:
(1 ) M a g n e t s u p p o r t s t r u c t u r e s h a v e b e e n o p t i m i z e d by
m e a n s of F E M n u m e r i c a l s i m u l a t i o n s for m a x i m u m
stiffness a n d high e i g e n f r e q u e n c i e s , m i n i m i z i n g t h e
influence of g r o u n d m o t i o n s a n d their a m p l i f i c a t i o n
on t h e e l e c t r o n b e a m [ 1 ] .
has been
alignment
inis
MONITORING HORIZONTAL POSITIONS OF THE
S L S S T O R A G E RING GIRDERS
T h e H P S m e a s u r e s relative m o v e m e n t s of the S L S
s t o r a g e ring g i r d e r s by u s i n g dial g a u g e s with linear
e n c o d e r s of the R e n i s h a w R G H 2 4 Z 5 0 A 0 0 A t y p e . T h e
resolution of the s e n s o r s is 0.5 urn a n d their w o r k i n g
r a n g e c o v e r s ± 2.5 m m . O n e a c h s i d e of a s e c t o r t h e
dial g a u g e s are t o u c h i n g r e f e r e n c e poles, w h i l e within
a s e c t o r the s e n s o r s are m o u n t e d on lever a r m s
b e l o w t h e b e n d i n g m a g n e t s (see Fig. 1). T h u s , the
H P S r e c o n s t r u c t s the virtual "train link", w h i c h is
f o r m e d by t h e m a g n e t positioning c o n c e p t of t h e S L S .
An
in-house
developed
low
cost
electronics
(< 1 k C H F / c h a n n e l )
interfaces
directly
into
the
E P I C S - b a s e d control s y s t e m , w h e r e the position
r e a d i n g s are a r c h i v e d . T h e c o m p l e t e s y s t e m w a s installed in the S L S s t o r a g e ring t u n n e l d u r i n g fall of
2 0 0 0 a n d is o p e r a t i o n a l s i n c e the b e g i n n i n g of 2 0 0 1 .
(2) Multipole m a g n e t s w e r e not a l i g n e d individually,
but w e r e p l a c e d in r e f e r e n c e t o precisely m a c h i n e d
a l i g n m e n t rails on t h e g i r d e r s [ 2 ] . W i t h t h e b e n d i n g
m a g n e t s bridging a d j a c e n t girders, a virtual "train
link" is f o r m e d a r o u n d the s t o r a g e ring.
(3) M o n i t o r i n g of vertical a s well as horizontal position
c h a n g e s of the g i r d e r s a n d B P M s t a t i o n s is prov i d e d by t h r e e i n d e p e n d e n t m e a s u r e m e n t s y s t e m s :
a h y d r o s t a t i c leveling s y s t e m ( H L S ) [ 3 ] , a h o r i z o n tal positioning s y s t e m ( H P S ) [ 3 ] , a n d a B P M p o s i tion m o n i t o r i n g s y s t e m ( P O M S ) [ 4 , 5 ] .
(4) R e p o s i t i o n i n g of t h e s t o r a g e ring g i r d e r s to t h e
d e s i r e d "train link" is p o s s i b l e t h r o u g h a girder
m o v e r s y s t e m [ 6 ] , w h i c h p r o v i d e s 2 urn resolution
within an o p e r a t i n g w i n d o w of ± 2.5 m m .
It is t h e r e f o r e possible to a p p l y a S V D (single v a l u e
decomposition) based dynamic alignment procedure
[ 7 ] , w h i c h a l l o w s t o c o r r e c t l o n g - t e r m drifts of s t o r a g e
ring c o m p o n e n t s m e c h a n i c a l l y . In this c a s e , H L S a n d
H P S are u s e d to d e t e r m i n e m i s a l i g n m e n t s a n d t h e
girder m o v e r s act a s c o r r e c t o r s . C o n s e q u e n t l y , it is
possible t o r e d u c e t h e a v e r a g e s t r e n g t h of t h e S L S
s t o r a g e ring c o r r e c t o r m a g n e t s , w h i c h are t h e n a g a i n
fully a v a i l a b l e for e l e c t r o n b e a m orbit c o r r e c t i o n s
within f e e d b a c k loops.
T h i s report p r e s e n t s first results of t h e H P S d u r i n g t h e
c o m m i s s i o n i n g period a n d early user o p e r a t i o n of the
S L S . T h e H P S data are c o r r e l a t e d to the s t o r a g e ring
t u n n e l t e m p e r a t u r e , w h i c h is e x p e c t e d t o c a u s e m o s t
of t h e drifts.
F i g . 1 : H P S set-up a n d s e n s o r .
Weekly Temperature Cycles
T h e t e m p e r a t u r e in the S L S s t o r a g e ring t u n n e l is
stabilized by a n air c o n d i t i o n i n g s y s t e m to a b o u t
± 0 . 1 °C [ 8 ] . Still, t e m p e r a t u r e c h a n g e s of a b o u t
0.5 °C are o b s e r v e d b e t w e e n w e e k l y o p e r a t i o n a n d
w e e k e n d s , w h e r e t h e m a c h i n e is u s u a l l y s h u t - d o w n .
S u c h typical t e m p e r a t u r e profiles of t h e s t o r a g e ring
t u n n e l are s h o w n in t h e u p p e r g r a p h s of Fig. 2 a n d 3.
A t i m e period b e t w e e n O c t o b e r a n d D e c e m b e r 2 0 0 1
h a s b e e n s e l e c t e d including t w o s h u t d o w n s inb e t w e e n ( w e e k s 4 2 a n d 4 3 / 2 0 0 1 a n d w e e k 4 6 / 2 0 0 1 ).
It is clearly visible, that t h e horizontal positions of the
g i r d e r s follow t h e t e m p e r a t u r e c y c l e s of t h e s t o r a g e
ring t u n n e l . T h e H P S s e n s o r s (in this e x a m p l e t h e
o n e s f r o m girder 1 of s e c t o r 0 6 a n d girder 2 of s e c t o r
07) show
readings
of up to ± 1 0 u m .
Since
c o r r e s p o n d i n g r e a d i n g s f r o m the H L S s y s t e m h a v e
29
not b e e n o b s e r v e d [ 9 ] , t h e H P S d a t a c a n be
interpreted as pure horizontal girder m o t i o n s . S e n s o r
r e a d i n g s t o t h e s a m e direction indicate d i s p l a c e m e n t s
(sector 0 6 ) , w h i l e r e a d i n g s in o p p o s i t e directions
p r e s u m e y a w s (sector 0 7 ) of t h e r e s p e c t i v e g i r d e r s .
U n d e r well s t a b i l i z e d t e m p e r a t u r e c o n d i t i o n s d u r i n g
the w e e k l y o p e r a t i o n periods, h o w e v e r , t h e H P S
r e a d i n g s p r o v e that t h e S L S s t o r a g e ring g i r d e r s a n d
t h u s a l s o t h e m a g n e t positions are stable o n a
m i c r o m e t e r level.
25
I
i
24
23
22
0.10
05.05.01
/
0.04
I
71ri
r:|...
iPdLT3
\—¡%|
0.00
-0.02
10/14/2001
10/30/2001
11/14/2001
11/30/2001
Time Period (Oct. 2001 - Dec. 2001)
12/16/2001
F i g . 2 : U p p e r g r a p h : t e m p e r a t u r e profile of s e c t o r 0 6
of the s t o r a g e ring t u n n e l d u r i n g a t i m e period
between
Oct.
and
Dec.
2 0 0 1 . Lower
graph:
c o r r e s p o n d i n g H P S d a t a f r o m girder 1 of sector 0 6 .
S e n s o r r e a d i n g s t o t h e s a m e direction indicate a
girder d i s p l a c e m e n t .
25.5
25.0
S 24.5
g- 24.0
P 23.5
0.10
0.08
— 0.06
•e
¡0.04
REFERENCES
[1]
P. W i e g a n d , S L S S R Girder: Vibration and
Analysis Tests, S L S - T M E - T A - 2 0 0 0 - 0 1 5 3 .
Modal
[2]
R. R u l a n d , S L S - H a n d b o o k , C h a p t e r 7.
[3]
V. S c h l o t t et al., Dynamic
Alignment
at
SLS,
Proc. E P A C ' 2 0 0 0 , V i e n n a , J u n e 2 0 0 0 . S e e also:
http://accelconf.web.cern.ch/accelconf/e00/PAPE
RS/WEP4A17.pdf
-r-
-HPS1-G2-Sec07
HPS2-G2-Sec07
..../y^\
.„
2L
[4]
V. Schlott, Monitoring
of Mechanical
Drifts at SLS
using Linear
Encoders,
PSI Scientific R e p o r t
1998, V o l u m e VII.
[5]
V. S c h l o t t et al., Commissioning
of the
SLS
Digital BPM System, Proc. P A C ' 2 0 0 1 , C h i c a g o ,
J u n e 2 0 0 1 . S e e also:
http://accelconf.web.cern.ch/AccelConf/p01/PAP
ERS/WPAH134.PDF
[6]
P. W i e g a n d , S L S S R Girder Mover: Test of the
Control System, S L S - T M E - T A - 2 0 0 0 - 0 1 4 5 .
[7]
A. S t r e u n , Algorithms
for Girder Positioning,
TME-TA-1999-0016, October 1999.
[8]
W . J o h o , private c o m m u n i c a t i o n .
[9]
S. Z e l e n i k a , private c o m m u n i c a t i o n . S e e also:
/LA
V)
a 0.02
I
10/14/2001
10/20/2001 11/30/2001
For a c o r r e c t identification of girder m o t i o n s like roll
a n d pitch, b o t h H L S a n d H P S d a t a h a v e t o be c o n s i d e r e d . Still, a s u r v e y of s t o r a g e ring c o m p o n e n t s at t h e
e n d of t h e y e a r 2 0 0 1 c o n f i r m s substantial roll of g i r d ers in s o m e locations [10]. S u c h m o v e m e n t s s h o w up
in t h e H P S data as indicated in Fig. 4 . A detailed
a n a l y s i s of m e c h a n i c a l d i s p l a c e m e n t s in t h e s t o r a g e
ring t u n n e l a n d tests w i t h d y n a m i c a l i g n m e n t are
s c h e d u l e d for the y e a r 2 0 0 2 .
s.
ö o.oo
-0.02
09.08.01
F i g . 4 : L o n g - t e r m drift of girder 3 of s e c t o r 0 7 .
HPS2-G1-Sec06
, 0.06
06/16/2001 07/27/2001
Time Period (Year 2001 )
-HPS1-G1-Sec06
0.08
' 0.02
m
- Temp:06
10/30/2001
11/14/2001
11/302001
12/16/2001
Time Period (Od. 2001 - Dec. 2001)
F i g . 3: U p p e r g r a p h : t e m p e r a t u r e profile of sector 0 7
of t h e S L S s t o r a g e ring t u n n e l during t h e s a m e t i m e
period as in f i g . 2. L o w e r g r a p h : c o r r e s p o n d i n g H P S
data f r o m girder 2 of sector 0 7 . R e a d i n g s of s e n s o r s
to o p p o s i t e directions indicate a y a w of the girder.
L o n g - t e r m Drifts
A p a r t f r o m t h e w e e k l y t e m p e r a t u r e c y c l e s , w h i c h are
e x p e c t e d t o d i s a p p e a r as s o o n as the S L S will b e o p e r a t e d w i t h o u t interruptions d u r i n g t h e w e e k e n d s , s u b stantial l o n g - t e r m drifts of s o m e girders in t h e s t o r a g e
ring h a v e b e e n m e a s u r e d by t h e H P S during t h e y e a r
2001.
S. Z e l e n i k a , Status
of the HLS System,
Scientific R e p o r t 2 0 0 1 , V o l u m e V I I .
[10] F. W e i , Survey and Magnet Position
Scientific R e p o r t 2 0 0 1 , V o l u m e V I I .
Stability,
SLS-
PSI
PSI
30
STATUS OF THE H LS SYSTEM
S.
Zelenika
The experience
gained so far on the Hydrostatic
Levelling System shows that micrometric
range
accuracies are indeed achievable,
creating the preconditions
for the beam-based
alignment
mode of operation of
the SLS storage ring. However, the long-term behaviour
of the HLS system is characterised
by
significant
drifts. The progress achieved so far in establishing
the causes of such behaviour is briefly
outlined.
INTRODUCTION
T h e capacitive proximity g a u g e - b a s e d H y d r o s t a t i c
Levelling S y s t e m ( H L S - Fig. 1) w a s d e v e l o p e d by t h e
E. M e i e r & Partner c o m p a n y as part of t h e S L S stora g e ring position m o n i t o r i n g s y s t e m with t h e final g o a l
of h a v i n g a reliable vertical position f e e d b a c k signal
for t h e f o r e s e e n b e a m - b a s e d a l i g n m e n t m o d e of o p eration.
All t h e p r e l i m i n a r y results s h o w e d that t h e a i m e d m i crometric range resolutions a n d accuracies have been
r e a c h e d [1]. H o w e v e r , t h e l o n g - t i m e b e h a v i o u r of the
H L S s y s t e m h a s r e v e a l e d drifts of c o n s i d e r a b l e m a g nitude.
[1] h a v e b e e n met, a n d t h e r e f o r e this m o d e of o p e r a tion will be t e s t e d in t h e near f u t u r e .
Long-term behaviour
T h e l o n g - t e r m b e h a v i o u r of the H L S r e a d i n g s , important t o m o n i t o r the s t o r a g e ring position stability a n d
t h u s to e v e n t u a l l y a l l o w t h e m a i n t e n a n c e of t h e stora g e ring location in s p a c e b a s e d o n s e n s o r s rather
t h a n traditional t o p o g r a p h i c i n s t r u m e n t s , h a s s h o w n
millimetre r a n g e drifts on s e v e r a l pots a l r e a d y after
f e w w e e k s of o p e r a t i o n (Fig. 2) [3].
0.25 x -
E
E,
ID
O)
c
'•5
(B
O-rings
o
a
49
sensor
plate
touching
point
F i g . 1 : S c h e m a t i c r e p r e s e n t a t i o n of the H L S pot interior.
SHORT- AND LONG-TERM BEHAVIOUR OF THE
HLS
Short-term behaviour
T h e H L S s y s t e m w a s put into o p e r a t i o n in the last
quarter of the y e a r 2 0 0 0 . S i n c e t h e n , p r e l i m i n a r y tests
on t h e b e h a v i o u r of t h e s y s t e m c o m p a r e d to laser
tracker and mover encoder measurements
have
s h o w n that t h e H L S allows t o a c h i e v e reliable m i c r o metric a c c u r a c y data with relative errors in t h e 1 %
r a n g e . T h e only d r a w b a c k s e e m s to be the relatively
long settling t i m e s n e e d e d t o a c h i e v e t h e c o r r e c t
r e a d i n g s o n t h e h e a v e , s i n c e in this c a s e t h e w a t e r
c o n t a i n e d in t h e H L S pots of t h e m o v e d girders h a s to
f l o w in/out f r o m t h e w h o l e s t o r a g e ring. In t h e c a s e of
pitch a n d roll m o t i o n s , t h e w a t e r is basically redistributed only in the H L S pots of t h e m o v e d girder, limiting
the settling t i m e s t o less t h a n 5 m i n [2].
T h e results of the p e r f o r m e d tests indicate t h u s that
the p r e c o n d i t i o n s t o a c h i e v e b e a m - b a s e d a l i g n m e n t
65
97
113
129
145
161
177
Pot number
F i g . 2 : Relative c h a n g e of t h e r e a d i n g s on all pots of
t h e s t o r a g e ring d u r i n g 3 w e e k s in s p r i n g 2 0 0 1 .
S o m e of t h e o b s e r v e d drifts h a v e b e e n t r a c e d b a c k to
t h e p o o r fixation a n d a l i g n m e n t of t h e piping n e t w o r k
w h i c h , w h e n c o u p l e d w i t h the rather h i g h w a t e r level
in t h e pipes at that t i m e , has led t o t h e c r e a t i o n of a
Bernoulli t u b e effect, i.e. t o t h e m o n i t o r i n g of t h e local
p r e s s u r e differences b e t w e e n t h e t h u s c r e a t e d t u b e
sections.
H o w e v e r , e v e n w h e n a d d i t i o n a l pipe s u p p o r t s h a v e
b e e n a d d e d , t h e p r o b l e m s still p e r s i s t e d . It w a s t h u s
s u p p o s e d that this p h e n o m e n o n c o u l d be d u e t o t h e
e v e n t u a l f o r m a t i o n of f o g a b o v e the w a t e r level, w h i c h
c o u l d influence t h e r e s p e c t i v e dielectric c o n s t a n t [3]. A
t h o r o u g h s t u d y of the t h e o r e t i c a l a s p e c t s of the airw a t e r m i x t u r e s has a l l o w e d t o e x c l u d e this as t h e
p o s s i b l e c a u s e of the p r o b l e m s .
H e n c e , it b e c a m e i n c r e a s i n g l y clear that t h e o b s e r v e d
drifts w e r e not r e l a t e d t o t e m p e r a t u r e or p r e s s u r e
effects at the pots t h e m s e l v e s , but rather to h u m i d i t y
build-up s o m e w h e r e at t h e g u a r d - t o - s e n s o r interface
( p r o b a b l y at t h e insulator c e r a m i c b e t w e e n t h e s e t w o
c o m p o n e n t s - s e e Fig. 1), w h i c h results in a parasitic
capacitance.
S i n c e t h e c h a n g e of the material of the insulator plate
(glass, q u a r t z a n d different t y p e s of c e r a m i c s h a v e
b e e n tried) did not a l l o w t o s o l v e the p r o b l e m [3], a
31
trial to a d d a silicone O-ring b e t w e e n t h e g u a r d a n d
the s e n s o r (Fig. 1), t h u s h i n d e r i n g t h e h u m i d i t y p a t h to
the c e r a m i c insert, w a s p e r f o r m e d a n d h a s led t o e n c o u r a g i n g results. In fact, a n initial p r o t o t y p e series of
15 p o t s m o d i f i e d with t h e additional O-ring s h o w e d
r e a d i n g s stable w i t h i n ± 1 0 urn ( w h i c h w a s the req u i r e d a c c u r a c y r a n g e ) o v e r s e v e r a l w e e k s . All t h e
pots h a v e t h e r e f o r e b e e n m o d i f i e d a c c o r d i n g l y .
In o r d e r t o investigate t h e s e h y p o t h e s e s , t h e f o l l o w i n g
m o d i f i c a t i o n s h a v e b e e n tried:
•
O n s o m e pots h o l e s h a v e b e e n a d d e d t o t h e
g u a r d s to facilitate t h e e v a p o r a t i o n of h u m i d i t y
r e a c h i n g t h e c e r a m i c plates. T h e results o b t a i n e d
show meaningful improvements.
•
T h e a d o p t i o n of longer c e r a m i c plates (bringing
t h e s e n s o r s closer t o t h e w a t e r s u r f a c e ) s e e m s t o
i n c r e a s e the stability of the results (especially if
c o m b i n e d w i t h t h e a b o v e m e n t i o n e d h o l e s in t h e
g u a r d s ) , w h i c h c o u l d be r e l a t e d to t h e i n c r e a s e d
level of the signal ( c a p a c i t a n c e ) b e i n g m e a s u r e d
in this c a s e .
•
S o m e pots h a v e b e e n t r e a t e d with disinfecting
m e d i a ("fungi killers") leading t o uncertain results.
•
T o t h e d e m i n e r a l i s e d w a t e r u s e d as the w o r k i n g
fluid in t h e H L S , an alcohol solution is a d d e d , a n d
t h e fluid level is t h e n i n c r e a s e d up t o the point
w h e r e t h e s e n s o r / g u a r d s u r f a c e s are f l u s h e d w i t h
it. It is h o p e d that this action c o u l d kill the m y cells, a n d t h e p r e l i m i n a r y results of s u c h trials
s e e m t o be e n c o u r a g i n g .
-5.70
6.8.01
20.8.01
3.9.01
17.9.01
1.10.01
15.10.01
Time
F i g . 3: R e a d i n g s o n a stable pot o v e r 2.5 m o n t h s . T h e
ripples (± 20 urn r a n g e ) that c a n be o b s e r v e d are
p r o b a b l y attributable t o real g r o u n d m o t i o n .
D e s p i t e t h e g o o d results o b t a i n e d initially w i t h t h e
d e s c r i b e d s o l u t i o n , after a t i m e period o n t h e m o n t h s
s c a l e , r o u g h l y half of t h e pots r e m a i n e d stable (Fig. 3)
w h i l e t h e o t h e r half started drifting a g a i n (Fig. 4). S e v eral trials w e r e p e r f o r m e d to try t o s o l v e the o b s e r v e d
p r o b l e m . A n a t t e m p t to c o m p e n s a t e for t h e drifts
electronically w a s not s u c c e s s f u l . T h e introduction of
silica-gel at t h e pots' e l e c t r o n i c s level w a s a l s o p r o v e n
to be u n s u c c e s s f u l [3].
S e v e r a l of t h e s e tests are still u n d e r w a y but, g i v e n
t h e high t i m e c o n s t a n t n e e d e d t o obtain a n y m e a n ingful results, no final c o n c l u s i o n is available yet.
CONCLUSIONS
T h e H L S s y s t e m h a s p r o v e n t o be an a c c u r a t e tool for
m o n i t o r i n g t h e s h o r t - t e r m positioning of the g i r d e r s ,
c r e a t i n g t h u s t h e p r e c o n d i t i o n s for t h e b e a m - b a s e d
a l i g n m e n t m o d e of o p e r a t i o n of the S L S s t o r a g e ring.
H o w e v e r , the s y s t e m p r o v e d not t o be reliable o n t h e
l o n g e r t i m e s c a l e s , h i n d e r i n g t h e possibility t o u s e it
a s a m o n i t o r of g e o l o g i c a l a n d t h e r m a l d i s t u r b a n c e s of
t h e s t o r a g e ring positions. S e v e r a l trials are u n d e r
w a y in o r d e r t o t a c k l e this p r o b l e m .
REFERENCES
24.6.01
29.7.01
2.9.01
7.10.01
Time
F i g . 4 : E x a m p l e of a drifting pot. It is w o r t h noticing
that t h e a n a l o g u e v a l u e s on all t h e drifting pots are
drifting t o t h e s a m e direction.
Two hypotheses have thus been formulated:
•=> T h e p r o b l e m c o u l d be d u e t o t h e residual h u m i d i t y
p a s s i n g t h r o u g h the O-ring (silicone h a s a w a t e r
a b s o r p t i o n of c a . 0.2 % ) a n d still b e i n g acc u m u l a t e d at t h e g u a r d - t o - s e n s o r interface at the
level of t h e c e r a m i c plate.
•=> T h e r e a s o n for t h e drifts c o u l d b e attributed t o t h e
m y - c e l l s of t h e f u n g i o b s e r v e d u n d e r a m i c r o s c o p e
on t h e s u r f a c e s of both the s e n s o r s a n d t h e
guards. T h e my-cells could then create "water
c h a n n e l s " (the p r o b l e m is t h e r e f o r e e v e n in this
c a s e , at least indirectly, related to h u m i d i t y effects)
i n d u c i n g a g a i n a parasitic c a p a c i t a n c e .
[1]
S. Z e l e n i k a et. al, The SLS Storage Ring
Support
and Alignment
Systems,
N u c l e a r Instr. M e t h .
P h y s . R e s . A 4 6 7 - 4 6 8 , pp. 99-102 (2001).
[2]
A. S t r e u n , Private
Communication.
[3]
E. Meier, Private
Communications.
32
BEAM-BASED ALIGNMENT MEASUREMENTS
M.
Böge
First beam-based
alignment measurements
have been carried out at the SLS storage ring which allow to calibrate the zero readings of the 72 BPMs with respect to the magnetic centers of adjacent quadrupoles.
The
presented results show that the vertical quadrupole-BPM
offsets are gaussian distributed with a standard
deviation of 0.24 mm.
quadrupole
INTRODUCTION
BPM
T h e B P M stations in t h e S L S s t o r a g e ring a r e rigidly
a t t a c h e d t o t h e girders a n d s e r v e a s s u p p o r t s for t h e
v a c u u m s y s t e m . A c c o r d i n g t o t h e s p e c i f i c a t i o n s of t h e
B P M s u p p o r t a n d t h e s t r a i g h t n e s s rulers o n t h e girders, t h e q u a d r u p o l e - B P M offsets a r e k n o w n t o within
± 5 0 / i m [1]. T h e p r e s e n t e d b e a m - b a s e d a l i g n m e n t
t e c h n i q u e allows t o m e a s u r e t h e s e offsets for t h e a d j a c e n t q u a d r u p o l e - B P M c o m b i n a t i o n s with / i m p r e c i s i o n .
T h e s e offsets c a n b e u s e d t o calibrate t h e m e c h a n ical positioning s y s t e m ( P O M S ) w h i c h m o n i t o r s relative position c h a n g e s of B P M s with respect t o a d j a c e n t
q u a d r u p o l e s u s i n g linear e n c o d e r s [2].
beam with bump
......3».
beam
} bpm
\
y
J;__V bpmJ
y
y
q
BEAM-BASED ALIGNMENT (BBA) PROCEDURE
F i g . 1 : Illustration of t h e b e a m - b a s e d a l i g n m e n t t e c h n i q u e a p p l i e d t o t h e q u a d r u p o l e s with a d j a c e n t B P M s .
T h e a p p l i e d m e t h o d [3, 4] is b a s e d o n t h e well k n o w n
fact that if t h e s t r e n g t h of a single q u a d r u p o l e q in t h e
ring is c h a n g e d , t h e resulting difference in t h e c l o s e d
orbit Ay(s) is p r o p o r t i o n a l t o t h e original offset y of t h e
b e a m at q.
BBA RESULTS
q
T h e e q u a t i o n for t h e resulting difference orbit is:
Ay"(s)
- (k(s) + Ak(s))Ay(s)
=
Ak(s)y (s).
0
T h e difference orbit is t h u s given by t h e c l o s e d orbit form u l a for a single kick, but c a l c u l a t e d w i t h t h e p e r t u r b e d
optics including Afc(s). F r o m t h e m e a s u r e d difference
orbit t h e kick a n d t h u s y c a n b e easily d e t e r m i n e d a n d
c o m p a r e d t o t h e n o m i n a l orbit y
in t h e B P M a d j a c e n t
t o t h e q u a d r u p o l e , yielding t h e offset b e t w e e n B P M a n d
q u a d r u p o l e axis. T h e precision of t h e m e t h o d is v e r y
m u c h i m p r o v e d by t a k i n g difference orbit d a t a for several local b e a m positions y v a r i e d with a n orbit b u m p .
T h e principle of t h e m e t h o d is illustrated in Fig. 1. T h e
error of t h e n o m i n a l position y
for w h i c h t h e b e a m
g o e s t h r o u g h t h e c e n t e r of t h e q u a d r u p o l e is t h e n g i v e n
by t h e resolution of t h e B P M s y s t e m . In t h e S L S stora g e ring, a difference orbit with a n a m p l i t u d e of 5 / i m
c a n b e clearly r e s o l v e d [5]. T h i s results in a resolution for t h e local kick of « 0 . 2 5 /¿rad for q u a d r u p o l e s
at vertical b e t a v a l u e s of 2 0 m . S i n c e a c h a n g e in
q u a d r u p o l e s t r e n g t h of Akl = 0.02 r r r c a u s i n g a t u n e
variation 5v = 0.03, is possible w i t h o u t losing t h e b e a m ,
a m i n i m u m b e a m offset of y ¿ „ = 15 /¿m c a n b e e a s ily d e t e c t e d . Taking several d a t a points by v a r y i n g a
local b u m p , t h e q u a d r u p o l e - t o - B P M a l i g n m e n t c a n b e
d o n e w i t h a precision of « 5 / i m . H o w e v e r s o m e of t h e
q u a d r u p o l e s a r e at low b e t a v a l u e s of 2 . 5 m w h i c h red u c e s t h e precision of t h e m e a s u r e m e n t t o « 4 0 / i m .
q
o p m
q
b p m
1
9 > m
In o r d e r t o h a v e a well d e f i n e d t u n e variation
{5v = ± 0 . 0 2 5 ) d u r i n g t h e b e a m - b a s e d a l i g n m e n t m e a s u r e m e n t , t h e previously m e a s u r e d a v e r a g e b e t a f u n c tions [6] a r e u s e d t o d e t e r m i n e t h e a l l o w e d c h a n g e of
q u a d r u p o l e s t r e n g t h . A hysteresis c o r r e c t i o n restores
0.014 r
ARfDI-BPÏVl-O/'yEfit(offset = 47.5 + - 0.5nm) -
0.012 CM
£
o
0)
o
c
<
<D
D
0.01 -
local b u m p s c a n
0.008 0.006 -
B P M offset
0.004 -
47.5u.rn
0.002 -
-0.4
-0.3
-0.2
-0.1
0
Ybpm
l
0.1
m m
0.2
0.3
0.4
l
F i g . 2 : B B A d a t a for B P M A R I D I - B P M - 0 7 M E s h o w i n g a
vertical B P M offset of 4 7 . 5 /¿m w i t h respect t o t h e a d j a c e n t q u a d r u p o l e A R I M A - Q M D - 0 7 at a b e t a function of
18 m .
t h e orbital t u n e s after e a c h q u a d r u p o l e variation c y c l e ,
in o r d e r t o m i n i m i z e t h e residual distortions of t h e linear
optics.
Fig. 2 s h o w s t h e result of a single vertical B P M offset
m e a s u r e m e n t for A R I D I - B P M - 0 7 M E . After t a k i n g a refe r e n c e orbit, t h e a d j a c e n t q u a d r u p o l e A R I M A - Q M D - 0 7
33
is c h a n g e d by Akl = 0.017 m
followed by a variation of a local orbit b u m p of ± 0 . 4 m m . T h e s q u a r e of
t h e s t a n d a r d deviation of t h e difference orbit, e x c l u d ing A R I D I - B P M - 0 7 M E , v e r s u s t h e B P M reading is fitt e d by a p a r a b o l a . T h e difference b e t w e e n t h e minim u m of t h e fit a n d t h e z e r o r e a d i n g of t h e B P M d e t e r m i n e s t h e B P M offset. In this c a s e t h e m e a s u r e m e n t reveals an offset of 4 7 . 5 ¡im within a n error of
± 0 . 5 um. Fig. 3 s u m m a r i z e s t h e result for 6 6 vertical B P M offsets with m e a s u r e m e n t error v a r i a t i o n s bet w e e n < 1 urn a n d 5 0 pm. T h e offset distribution is
fitted by a g a u s s i a n shifted by - 0 . 1 1 m m with a s t a n d a r d deviation of 0.24 m m . T h r e e B P M s s h o w offsets
larger t h a n 0.5 m m . T h e offsets h a v e b e e n fed into
_
—i
1
present kick
kick change
sum kick
0.4 -
1
—
Q
. ! • ¡P r
hipli. i il (¡i
50
100
150
200
250
s fml
F i g . 4:
C o m p a r i s o n of actual c o r r e c t o r settings
("present kick") for a flat orbit a n d p r e d i c t i o n s for t h e
c o r r e c t i o n of t h e vertical B P M offsets ("kick c h a n g e " )
indicating a possible R M S kick r e d u c t i o n of 2 0 % . T h e
s q u a r e s ( " s u m kick") d e n o t e t h e differences.
OUTLOOK
1
'-.
1
fit (<y>=-0,11 mm, V<y'>=0,24 mm)
Several B B A m e a s u r e m e n t s h a v e b e e n p e r f o r m e d in
2 0 0 1 indicating a n B P M offset variation of « 10 % over
several m o n t h s . D u e t o path length effects in t h e horizontal plane, t h e p r e s e n t e d m e t h o d n e e d s t o b e m o d i fied in o r d e r t o d e t e r m i n e t h e horizontal B P M offsets.
T h e "dynamic" beam-based alignment based on the
m o d u l a t i o n of q u a d r u p o l e c u r r e n t s , at < 1 0 Hz [7], o b s e r v i n g t h e m o d u l a t i o n f r e q u e n c y c o m p o n e n t in t h e resulting orbit [8] h a s not b e e n c a r r i e d out yet.
REFERENCES
[1 ] F. Q. W e i et al., SLS Survey and Alignment
PSI Scientific R e p o r t 2 0 0 0 , V I I .
in 2000,
[2] V. Schlott, Monitoring
of Mechanical
Drifts at SLS
Using Linear Encoders, PSI Scientific R e p o r t 1998,
VII.
-0.5
0
vertical BPM offset Tmrnl
F i g . 3: Vertical B P M offsets with respect to a d j a c e n t
q u a d r u p o l e s in t h e S L S s t o r a g e ring. T h e offset distribution is fitted by a g a u s s i a n shifted by - 0 . 1 1 m m w i t h
a s t a n d a r d deviation of 0.24 m m . T h e m e a s u r e m e n t
error v a r i e s b e t w e e n < 1 pm a n d 5 0 pm.
a n S V D b a s e d global orbit c o r r e c t i o n c o d e in o r d e r to
determine the corresponding corrector pattern. T h e s e
c o r r e c t o r p r e d i c t i o n s ("kick c h a n g e " ) c a n b e c o m p a r e d
t o t h e actual c o r r e c t o r settings ("present kick") for a flat
orbit. Fig. 4 d e p i c t s both p a t t e r n s a n d their difference
( " s u m kick"). It c a n b e s e e n that they a r e "anticorrelated" resulting in a 2 0 % r e d u c t i o n of t h e R M S c o r r e c tor kick f r o m 0.15 m r a d to 0.12 m r a d . F u r t h e r m o r e t h e
m e a n c o r r e c t o r kick of - 0 . 0 1 4 m r a d is r e m o v e d .
[3] P. Röjsel, A Beam Position Measurement
System
Using Quadrupole
Magnets Magnetic Centra as the
Position Reference,
Nucí. Instr. M e t h . , A 3 4 3 , 1994.
[4] R. B r i n k m a n n , M. B ö g e , Beam-Based
and Polarization
Optimization
in the HERA
Ring, Proc. EPAC 9 4 , L o n d o n , 1994.
Alignment
Electron
[5] V. Schlott et al., Digital BPM System - Proof of Functionality, PSI Scientific R e p o r t 2 0 0 0 , V I I .
[6] M. B ö g e , A. S t r e u n , Measurement
tion of Linear Optical Distortions,
port 2 0 0 1 , V I I .
and
CompensaPSI Scientific R e -
[7] H. U. B o k s b e r g e r et al., Power
Supplies
for
SLS,
PSI Scientific R e p o r t 1999, V I I .
[8] R. S c h m i d t , Misalignments
from
k-Modulation,
Proc. 3 r d W o r k s h o p o n L E P P e r f o r m a n c e , C E R N
S L / 9 3 - 1 9 , 1993.
34
HIGH LEVEL SOFTWARE AND OPERATOR INTERFACE
A. Lüdeke,
M. Böge,
d. Chrin
The commissioning
of the Swiss Light Source, including the first four insertion devices, was
accomplished
within a time period of 18 months. First user operation
was already manifest
before the official end of
commissioning
in August 2001. Integration
of all subsystems
into the control system and a high degree of
automation
was a prerequisite
to meeting the tight time schedule.
A balanced distribution
of
functionality
between high level and low level applications
allowed for short development
cycles and added to the high
reliability and reproducibility
of applications.
Essential high level procedures,
once verified, were
encapsulated and migrated
to lower levels whenever
feasible. This served to reduce the number of
parameters
required to set-up the machine and allowed standard EPICS tools to be used for the display, archiving
and
processing
of complex physical
values.
INTRODUCTION
T h e c o n s t r u c t i o n a n d c o m m i s s i o n i n g of t h e S w i s s
Light S o u r c e w a s c o m p l e t e d within a v e r y tight t i m e
s c h e d u l e . T h e t o p priority w a s to deliver a p p l i c a t i o n s in
d u e t i m e a n d to a p p l y e n h a n c e m e n t s on t h e fly
w h e n e v e r n e e d e d during c o m m i s s i o n i n g . C e r t a i n s u b s y s t e m s , including c o r r e s p o n d i n g high level a p p l i c a tions, w e r e delivered by external c o m p a n i e s s u b s y s t e m s , e.g. t h e Linac a n d t h e 5 0 0 MHz R F - s y s t e m .
APPLICATION ENVIRONMENT
T h e application e n v i r o n m e n t , s h o w n in Fig. 1, w a s
c h o s e n to e n a b l e a fast a n d flexible d e v e l o p m e n t of
high level a p p l i c a t i o n s .
GUI
Cfavaj
Corba
3
GUI
Server
GUI
Wftk)
Corba
î
Model
I
CDEV
î
C
D
E
V
~cÄ~
;
¡
Gateway
CA
f
OrbiO Oracle.
-Server'
FB
.-Analysis. -""Tracy\ Server •' -Servar
Beam Dynamics
Environment
GUI
GUI
GUI
(tciflN) tmedm) ODD
CDEV I CA
CA
Gateway
CA
EPICS records
SNL
device/driver
sub
"Hardware"
(DSPs, Controllers, SPS,...)
Controls
Environment
F i g . 1 : T h e S L S application e n v i r o n m e n t .
A p p l i c a t i o n s in the " C o n t r o l s E n v i r o n m e n t " u s e t h e
C o m m o n D e v i c e ( C D E V ) m i d d l e - w a r e [1]. C o n t r o l
functionality is i m p l e m e n t e d in the
Experimental
P h y s i c s a n d Industrial Control S y s t e m ( E P I C S ) [2], a
tool-kit t o build large, distributed control s y s t e m s , d e v e l o p e d a n d m a i n t a i n e d by a large c o l l a b o r a t i o n .
The beam dynamics group has developed a C o m m o n
Object Request Broker Architecture ( C O R B A ) envir o n m e n t to s u p p o r t their n e e d s for multiple c o n n e c tivity. T h e s o called model-server
p r o v i d e s for the
graphical user interfaces ( G U I s ) as well a s o t h e r client/server a p p l i c a t i o n s a c c e s s t o t h e E P I C S b a s e d
control s y s t e m , the O r a c l e d a t a b a s e , t h e T r a c y a c c e l erator s i m u l a t i o n tools a n d a n e v e n t server. Details of
this e n v i r o n m e n t c a n be f o u n d in [3].
OPERATOR INTERFACE
M a n y generic a p p l i c a t i o n s f r o m t h e E P I C S c o l l a b o r a tion w e r e put t o g o o d effect at the S L S . A p p l i c a t i o n s
for handling a l a r m s , s a v i n g a n d restoring m a c h i n e setu p s , archiving data a n d building G U I s w e r e a l r e a d y
m a d e available. M a n y o t h e r applications, including
m o s t of the p h y s i c s applications, w e r e h o w e v e r d e v e l o p e d i n - h o u s e . T h e c o n t r a c t o r s for t h e Linac a n d the
5 0 0 M H z R F s y s t e m a l s o delivered G U I s for their
systems.
T h e variety of i n d e p e n d e n t prototype high level a p p l i c a t i o n s , d e v e l o p e d during c o m m i s s i o n i n g , led t o a
diversity of o p e r a t o r interfaces. A style g u i d e w a s e s t a b l i s h e d t o simplify their u s a g e , e.g. help m e n u s for
accessing web documentation. Nevertheless, since
t h e p r o g r a m m i n g l a n g u a g e s u s e d varied in their s u p port for G U I building b l o c k s , a p p e a r a n c e s still differed
considerably
between
applications.
Furthermore
m a i n t e n a n c e of c u s t o m i z e d G U I s is likely to prove
t i m e c o n s u m i n g in t h e long t e r m .
T o help t a c k l e t h e s e p r o b l e m s , essential p r o c e d u r e s
are d e c o u p l e d f r o m t h e G U I a n d , o n c e verified, are
m i g r a t e d t o low level a p p l i c a t i o n s w h e r e v e r feasible.
T h e s e low level a p p l i c a t i o n s are i m p l e m e n t e d either
a s a s e r v e r a p p l i c a t i o n in the C O R B A e n v i r o n m e n t
a n d / o r a s an E P I C S d a t a b a s e r e c o r d resident in V M E .
O p e r a t o r Interfaces c a n c o n s e q u e n t l y be r e p l a c e d by
m o r e g e n e r i c application built f r o m a c o m m o n set of
GUI widgets.
EXAMPLE: MAGNET OPTICS CONTROL
A particular f e a t u r e of the S L S s t o r a g e ring is the individual p o w e r i n g of all 174 q u a d r u p o l e m a g n e t s . T h i s
allows v e r y flexible a d j u s t m e n t s of the f o c u s i n g at the
e x p e n s e of i n c r e a s e d p a r a m e t e r s p a c e . F r o m t h e start
of the ring c o m m i s s i o n i n g , a n Interactive Data L a n g u a g e (IDL) G U I (see Fig. 2 ) w a s u s e d t o set elem e n t s of t h e m a g n e t optics t o v a l u e s b a s e d o n t h e o retical calculations. A f e w optics p a r a m e t e r s c o u l d
t h e n be a d j u s t e d for the online t u n i n g of the m a c h i n e .
35
EXAMPLE: LIFETIME CALCULATION
Ü5IÍ
Storage Bong Optics Müde : d2e ^
: shift gx lir o.ooaooooü
: S h i f t CXby jil.OOOOO
: : - 0.OS! - D.Oll reset! » D.0l{ . 0.OS!
- 0.5
- D.l{ r e l e t
T h e e l e c t r o n b e a m lifetime w a s c a l c u l a t e d f r o m a p r e cise c u r r e n t m e a s u r e m e n t , using a V o l t m e t e r r e a d o u t
via G P I B , with an u p d a t e period of t w o s e c o n d s .
Sextupole
Correction
* O.ll * 0.5
i shift gr ir jo.250000
1
__!__1 iiJLÜil
lteset
j _ _ y ______
Shift CY by jO.50O000
- 0.5
- O.l! reset
!j jjJWllj i_>JJ)lj
* O.ll * 0.5
F i g . 2 : M a g n e t o p t i c s application "Tset"
M a c h i n e optics w e r e first s e l e c t e d f r o m a m e n u butt o n . A d j u s t a b l e p a r a m e t e r s i n c l u d e d : horizontal- a n d
vertical t u n e shift, horizontal- a n d vertical c h r o m a t i c i t y
shift, a s e x t u p o l e - a n d a global e n e r g y s c a l i n g . T h e
n o m i n a l optics v a l u e s a n d all matrix p a r a m e t e r s required for the calculation of m a g n e t s e t - c u r r e n t s w e r e
c o d e d into t h e G U I . A n e l e c t r o n b e a m c o u l d c o n s e quently be s t o r e d a n d a c c u m u l a t e d within the first
d a y s of c o m m i s s i o n i n g .
O n e d r a w b a c k , h o w e v e r , w a s that t h e actual m a c h i n e
state w a s k n o w n only t o t h e a p p l i c a t i o n . O n c e the G U I
w a s c l o s e d , t h e r e w a s no e a s y w a y to d e d u c e t h e
actual optics f r o m t h e m a g n e t c u r r e n t settings. T h i s
w a s s o l v e d by m i g r a t i n g functionality t o an E P I C S
d a t a b a s e . T h e n o m i n a l m a g n e t c u r r e n t s of the o p t i c s
a n d the a d j u s t m e n t m a t r i c e s are n o w g e n e r a t e d by t h e
optics s i m u l a t i o n application in a s t a n d a r d E P I C S
s n a p s h o t f o r m a t . T h i s c a n be d o w n l o a d e d t o t h e m a c h i n e u s i n g s t a n d a r d s a v e a n d restore tools. T h e r e fore newly d e v e l o p e d optics c a n be easily a p p l i e d t o
the m a c h i n e , w i t h o u t t h e n e e d to c h a n g e application
c o d e . T h e actual settings of t h e m a c h i n e for a g i v e n
optics are t h u s r e d u c e d to a s m a l l n u m b e r of physical
p a r a m e t e r s that are m a p p e d to E P I C S c h a n n e l s .
S t a n d a r d E P I C S t o o l s c a n t h u s be u s e d to control,
s a v e , restore, archive a n d v i e w t h e s e c h a n n e l s . T h e
o p e r a t o r interface of the optics control is i m p l e m e n t e d
using t h e g e n e r i c p r o g r a m "panel.tcl" (see Fig. 3).
rile
Setup
Channels
A limitation h o w e v e r w a s that data w a s only g e n e r a t e d
w h i l e the G U I w a s r u n n i n g . T h e r e f o r e the a p p r o v e d
a l g o r i t h m w a s ported to C a n d i m p l e m e n t e d at a lowlevel a s an E P I C S d e v i c e s u p p o r t routine. All p a r a m e t e r s of t h e lifetime calculation are n o w available
t h r o u g h E P I C S c h a n n e l s that c a n be controlled a n d
r e a d by s t a n d a r d a p p l i c a t i o n s , r e m o v i n g the n e e d for
t h e c u s t o m i z e d lifetime G U I . T e s t s of an alternative
f a s t e r r e a d o u t of the c u r r e n t m e a s u r e m e n t are n o w in
p r o g r e s s . T h e i n c r e a s e d s a m p l e rate will allow lifetime
m e a s u r e m e n t s b e t w e e n injections w h e n in "top-up"
o p e r a t i o n m o d e [4].
SUMMARY
T h e m a i n goal of the a p p l i c a t i o n s d e v e l o p e d w a s to
e n a b l e t h e s u c c e s s f u l c o m m i s s i o n i n g of the light
s o u r c e in t i m e . T h e d e s i r e d functionality w a s d e l i v e r e d
in a t i m e l y m a n n e r a n d s h o w n to w o r k reliably.
T h e m a i n f o c u s of high level a p p l i c a t i o n s n o w is to
i m p r o v e the maintainability of the s y s t e m t h r o u g h inc r e a s e d modularity, i.e. by d e c o u p l i n g essential p r o c e d u r e s f r o m the G U I a n d t o s t a n d a r d i z e the o p e r a t o r
interface.
REFERENCES
Tune Shift Panel Me\
Used Optic Name
T h e c a l c u l a t i o n , c o n t r o l , test a n d c o m p a r i s o n of different a l g o r i t h m s w e r e i m p l e m e n t e d in a c u s t o m i z e d
J a v a a p p l i c a t i o n . T h e first s t e p in integrating this a p p l i cation t o the control s y s t e m w a s to e x p o r t the c a l c u lated lifetime to o t h e r a p p l i c a t i o n s via an E P I C S soft
c h a n n e l . T h i s already a l l o w e d s t a n d a r d E P I C S a p p l i c a t i o n s to be u s e d for archiving the lifetime for later
a n a l y s i s a n d to display lifetimes in a real-time strip
chart t o g e t h e r with o t h e r c o r r e l a t e d c h a n n e l s .
Info
Help
[1]
J . C h e n et al., An Object-Oriented
for
Developing
Device
Control
ICALEPCS 1995, Chicago, USA.
[2]
S.A. Lewis, The Experimental
Physics and
trial
Control
System,
LBNL,
April
http://csg.lbl.gov/EPICS/OverView.pdf
[3]
M. B ö g e , J . C h r i n , On the use of Corba in high
level beam dynamics applications
at the SLS, PSI
Scientific R e p o r t 2 0 0 1 , V o l u m e V I I .
[4]
M. M u ñ o z , Top-up operation,
port 2 0 0 1 , V o l u m e V I I .
D2R
Set Energy- (E-QS)
Bend Energy (E-B)
Use Energy from
h i i H n j y SI:HIIIII| HHI l u r
Choose Optic Panel /devl
Setup
Haine ni thf Optir
Hnminal hnnrgy
nominal nor. I une
nominal vur. Tuuu
lieV
.t. W)t
E OS
I .01
toggle
in
Qujdrupule SulUuqs
llnr. Tune Shift
10.000 J
Vur. lunu Slufl
I d . VI ."» .*
-
Suxlupolu Suturai:,
Mor. Chrom. Shift
Humiliai luir, f l i n m i H l .
Ver. Chrom. Shift
Humiliai ver. • ImmiHl.
Sextupol Scaling
10.COO *
Mi nil:.
F i g . 3: T h e g e n e r i c panel.tcl application, here c o n f i g ured for control of t h e S L S ring m a g n e t optics.
A notable a d v a n t a g e of this a p p r o a c h is that pertinent
m a c h i n e p h y s i c s data is s t o r e d in units that are
m e a n i n g f u l to t h e a c c e l e r a t o r physicist, rather t h a n in
units specific t o t h e native control s y s t e m .
Class
Library
Applications,
Indus2000,
PSI Scientific R e -
36
MEASUREMENT AND COMPENSATION OF LINEAR OPTICAL DISTORTIONS
M. Böge,
A.
Streun
In the SLS storage ring the measured
linear optical functions differ from the model predictions
because
of focussing
errors of the 174 quadrupoles.
In order to minimze these linear optical distortions
a SVD
based correction algorithm
has been implemented.
The algorithm
uses the quadrupoles
as "beta
function
correctors"
taking advantage of the fact that they are individually
powered. Residual beta beats of 4% in the
horizontal and 3 % in the vertical plane have been
obtained.
INTRODUCTION
In o r d e r to o p t i m i z e t h e p e r f o r m a n c e of t h e S L S s t o r a g e
ring a g o o d u n d e r s t a n d i n g of t h e linear optics is n e c e s sary. W h e n e v e r possible, k n o w n differences b e t w e e n
t h e real m a c h i n e a n d t h e u n d e r l y i n g m o d e l s h o u l d b e
m i n i m i z e d . For this r e a s o n , t h e 174 individually p o w e r e d q u a d r u p o l e s in S L S s t o r a g e ring h a v e b e e n u s e d
as " b e t a function c o r r e c t o r s " .
BETA FUNCTION MEASUREMENT
A n i m p o r t a n t ingredient for t h e s u c c e s s f u l c o m p e n s a tion of t h e linear optical distortions is t h e p r e c i s e m e a s u r e m e n t of t h e a v e r a g e b e t a f u n c t i o n s at t h e location
of t h e q u a d r u p o l e s . T h e p r e s e n t e d p r o c e d u r e m a k e s
u s e of t h e fact that a b e t a t r o n t u n e c h a n g e 5v is related
t o t h e p e r t u r b a t i o n 5k(s) of t h e f o c u s s i n g s t r e n g t h a n d
t h e b e t a function ß(s) a r o u n d t h e ring:
8v = -±-
ideal optics within t h e error of t h e b e t a m e a s u r e m e n t if
t h e q u a d r u p o l e s a r e t h e only s o u r c e of t h e optics perturbation.
RESULTS
Fig. 1 s h o w s t h e result of a b e t a c o r r e c t i o n r e d u c i n g t h e
b e t a beat in t h e horizontal a n d vertical p l a n e by a factor
of 2 with r e m a i n i n g b e a t s of « 4 % a n d « 3 % , r e s p e c tively. T h e q u a d r u p o l e s t r e n g t h variation Sk/k « 1.5e-3
with respect t o t h e d e s i g n s t r e n g t h k is c o n s i s t e n t with
m a g n e t m e a s u r e m e n t s [1].
jß(s)ök(s)ds.
T h u s a c h a n g e in t h e s t r e n g t h Sk(s ) of q u a d r u p o l e q
allows t h e a v e r a g e b e t a function ß(s )
at position s to
b e m e a s u r e d , by o b s e r v i n g 5v as a function of
Sk(s ).
T h e error of this m e a s u r e m e n t d e f i n e s t h e limit for t h e
c o r r e c t i o n of t h e linear optics p e r t u r b a t i o n s . T h u s a
sophisticated procedure has been implemented which
t a k e s into a c c o u n t k n o w n m a g n e t i c hysteresis effects
a n d restores t h e b e t a t r o n t u n e s rather t h a n t h e original q u a d r u p o l e c u r r e n t s . In a d d i t i o n , t h e q u a d r u p o l e s
a r e m e a s u r e d " m a g n e t family" w i s e in o r d e r t o m i n i m i z e
t h e residual optical p e r t u r b a t i o n s . In o r d e r t o i n c r e a s e
t h e precision further, t h e t u n e is o b s e r v e d for 5 different c u r r e n t s . T h e b e t a f u n c t i o n s a r e t h e n d e r i v e d f r o m
a least s q u a r e fit. A s a result a v e r a g e m e a s u r e m e n t
errors of « ± 1 % h a v e b e e n a c h i e v e d .
q
q
q
q
BETA CORRECTION A L G O R I T H M
T h e information a b o u t t h e horizontal a n d vertical b e t a
beat ößi at t h e position of t h e ¿th q u a d r u p o l e c a u s e d
by a s t r e n g t h p e r t u r b a t i o n Skj of t h e j ' t h q u a d r u p o l e is
c o n t a i n e d in t h e ( 2 * 1 7 4 ) x 1 7 4 sensitivity matrix S:
0
50
100
150
s [m]
200
250
F i g . 1 : M e a s u r e d a v e r a g e b e t a f u n c t i o n s ( s q u a r e s ) at
t h e location of 1 7 4 q u a d r u p o l e s in c o m p a r i s o n to t h e
m o d e l of t h e u n p e r t u r b e d optics (solid lines).
REFERENCES
w h i c h c a n b e d e r i v e d f r o m t h e m o d e l . A S i n g u l a r Value
D e c o m p o s i t i o n ( S V D ) t e c h n i q u e is t h e n u s e d t o "invert"
S a n d d e t e r m i n e t h e Skj as a f u n c t i o n of t h e ößi. F e e d ing -5kj into t h e " b e t a f u n c t i o n c o r r e c t o r s " restores t h e
[1] B. J a k o b , C h . Vollenweider, J . A. Zichy,
Production
and Measurement
of the Magnets for Booster
and
Storage Ring, PSI Scientific R e p o r t 1999, V I I .
37
COMMISSIONING RESULTS FOR THE SLS TRANSVERSE MULTIBUNCH
FEEDBACK
R. Bressanutti,
M. Dehler, P. Pollet, T. Schilcher,
V. Schlott
D. Bulfone, M. Lonza, L. Zambón (Sincrotrone
Trieste)
A wide band bunch-by-bunch
transverse
multi-bunch
feedback, developed
in collaboration
with
ELETTRA
(Sincrotrone
Trieste),
has been installed
at the SLS. We describe
the main hardware
and
software
components,
present the first commissioning
results and give the present status of the system as well as
an outlook on future
developments.
c u r r e n t s y s t e m w a s s e t u p a n d c o m m i s s i o n e d first for
t h e vertical plane.
INTRODUCTION
Beam
Beam.
F i g . 1 : Block d i a g r a m of S L S t r a n s v e r s e m u l t i - b u n c h
feedback.
The SLS Transverse Multi-Bunch Feedback System
[1] c o n s i s t s of a w i d e - b a n d b u n c h - b y - b u n c h s y s t e m ,
w h e r e t h e positions of the 4 8 0 b u n c h e s , s p a c e d 6 0 c m
(=2 n s e c ) apart, are c o r r e c t e d individually. W i d e b a n d
position signals c o m i n g f r o m a special t w o button B P M
p i c k u p are c o n v e r t e d to b a s e b a n d (0 - 2 5 0 M H z )
f o l l o w e d by s a m p l i n g with a fast 8 bit, 5 0 0 M S / s e c
A n a l o g - t o - D i g i t a l C o n v e r t e r ( A D C ) . In o r d e r t o be able
to p r o c e s s t h e data rate, de-multiplexig is u s e d
c o n v e r t i n g the 8 bit, 5 0 0 M S / s e c data flux t o 6 F P D P
(Front Panel D a t a Port) c h a n n e l s being 3 2 bit w i d e
a n d 21 M S / s e c fast.
E a c h c h a n n e l leads t o a m u l t i - p r o c e s s o r b o a r d
containing
four
TI-TMS320C6201
Digital
Signal
P r o c e s s o r s ( D S P ) . In the c u r r e n t s e t u p , o n e D S P
t a k i n g all the d a t a f r o m o n e of the c h a n n e l s
( c o r r e s p o n d i n g to 8 0 b u n c h e s ) s e r v e s for on-line
diagnostics, whereas the remaining three
DSP
c o n c u r r e n t l y calculate corrective kick v a l u e s .
T h e c u r r e n t D S P s o f t w a r e allows for setting of Finite
I m p u l s e R e s p o n s e ( F I R ) filters with up to 5 t a p s [2].
T h e m o s t basic d e s i g n is a 3 t a p filter, w h e r e the
coefficients are c h o s e n to reject the b e a m h a r m o n i c s
at the multiples of t h e revolution f r e q u e n c y a n d to
provide the right p h a s e at t h e b e t a t r o n f r e q u e n c y . T h e
f r e q u e n c y d e p e n d e n c y of s u c h a filter t o g e t h e r with
that of a m o r e a d v a n c e d 5 t a p filter h a v i n g a n
i m p r o v e d noise b e h a v i o u r is s h o w n in Fig. 2. T h e o p e n
loop d e l a y b e t w e e n B P M p i c k u p a n d kicker
comes
out t o be roughly 4 revolution periods.
bp. S i l i « .
yf-
j
. y
y
%
/^y
t \
,
-
.
\
\
•
f/fO
^
! ,
T
*
i is'S tîSSF ::::::::::
-
'4-vi
ö
"3
1
mo
Fig. 2: Amplitude and phase versus
normalized
f r e q u e n c y ( D e s i g n p h a s e - 5 0 d e g r e e s at a b e t a t r o n
t u n e of 0.18 m a r k e d by t h e d a s h e d line) for the basic 3
t a p filter (red) a n d a n o p t i m i z e d 5 tap filter ( g r e e n ) .
T h e kick data is r e c o m b i n e d following a s y m m e t r i c
multiplexing s c h e m e a n d t r a n s m i t t e d to a fast eight-bit
5 0 0 M S / s e c Digital-to-Analog C o n v e r t e r ( D A C ) . T h e
a n a l o g signal is a m p l i f i e d by a w i d e - b a n d R F p o w e r
amplifier before being applied t o the b e a m using a
stripline kicker. For the n e c e s s a r y s y n c h r o n i z a t i o n t o
the a c c e l e r a t o r s y s t e m , a flexible t i m i n g s y s t e m is
e m p l o y e d . A n o v e r v i e w of t h e w h o l e s y s t e m is s h o w n
in Fig. 1 .
CLOSED LOOP RESULTS
The
effect of m u l t i - b u n c h
instabilities
is
most
p r o n o u n c e d in the vertical plane, since e.g. resistive
wall i m p e d a n c e s are s t r o n g e r in that plane a n d t h e
b e a m size is s m a l l e r vertically t h a n horizontally. S o t h e
F i g . 3: Pin hole c a m e r a i m a g e s of a 8 0 m A b e a m with
f e e d b a c k off (left) a n d on (right). A basic 3 tap filter
algorithm was used.
38
T h e feedback has been characterized and the
f e e d b a c k loop c l o s e d . D u e t o an e r r o n e o u s protection
circuit in the p o w e r amplifiers, w h i c h s w i t c h e d off t h e
a m p l i f i e r s at higher c u r r e n t s , w e c o u l d a s yet run the
f e e d b a c k only at b e a m c u r r e n t s b e l o w 150 m A , a
restriction, w h i c h h a s b e e n r e m o v e d s i n c e . Fig. 3
s h o w s the effect of t h e f e e d b a c k o n t h e 8 0 m A b e a m
exhibiting vertical c o u p l e d - b u n c h instabilities a s s e e n
via a pin hole c a m e r a .
DIAGNOSTIC MEASUREMENTS
A n i m p o r t a n t a d v a n t a g e of the s y s t e m is t h e u s e of six
of t h e 2 4 D S P a s an on-line diagnostic tools. T h e s e
allow c o n c u r r e n t l y t a k i n g b u n c h - b y - b u n c h data w i t h o u t
disrupting the f e e d b a c k o p e r a t i o n .
8e+06
7e+06
6e+06
•e
<
5e+06
4e+06
•o
^ 3e+06
2e+06
1e+06
0 Ii
f/fO
F i g . 4 : C o u p l e d - b u n c h a m p l i t u d e s p e c t r a of a 8 0 m A
vertically instable b e a m with m u l t i - b u n c h f e e d b a c k
off/on. F r e q u e n c y is n o r m a l i z e d to the revolution
f r e q u e n c y (1.04 M h z ) of t h e b e a m .
In Fig. 4 , w e s e e a g a i n t h e effect of running with
f e e d b a c k o n a n d off, this t i m e in the Fourier s p e c t r u m
of the b e a m m o t i o n . Not t h e w h o l e s p e c t r u m f r o m 0 t o
2 4 0 t i m e the revolution f r e q u e n c y is s h o w n , but o n l y
the interesting r e g i o n , w h e r e w e h a v e c o u p l e d - b u n c h
m o d e s . T h e distribution of the f r e q u e n c i e s s e e m t o
indicate, that the d o m i n a n t c a u s e of t h e instabilities is
b u n c h - t o - b u n c h c o u p l i n g d u e to resistive l o s s e s in t h e
ring c h a m b e r .
5000
4500
4000
•4-.
<c
CD 2500
•o
2000
Q.
E 1500
<
Fast Ion Instability?
A b u n c h - b y - b u n c h T M B F s y s t e m b a s e d o n D S P s for
t h e p r o c e s i n g of the data c o m i n g f r o m all 4 8 0 b u n c h e s
in t h e S L S s t o r a g e ring h a s b e e n installed. A s of
today, c o m m i s s i o n i n g h a s only b e e n d o n e o n the
vertical plane. T h e s y s t e m h a s b e e n s h o w n to be a n
effective c u r e a g a i n s t c o u p l e d - b u n c h
instabilities
a l l o w i n g in addition for v a l u a b l e on-line d i a g n o s t i c s .
It w a s originally p l a n n e d t o h a v e t h e f e e d b a c k
o p e r a t i o n a l for all t h r e e p l a n e s . N o w , the p r o g r e s s of
t h e project h a s b e e n i m p e d e d by p r o b l e m s with the
o n l y available supplier of A D C a n d D A C b o a r d s , w h o
s t o p p e d selling t h e s e . S i n c e a l s o other a c c e l e r a t o r
laboratories e x p r e s s e d c o n s i d e r a b l e interest in t h e s e
c o m p o n e n t s , an i n - h o u s e d e v e l o p m e n t project for
t h e s e t y p e s of A D C s a n d D A C s h a s b e e n s t a r t e d . In
parallel, the last p r e p a r a t i o n s for t h e h a r d w a r e of the
longitudinal f e e d b a c k , amplifier a n d kicker, are d o n e .
T h e full s y s t e m , c o n s i s t i n g of t h r e e f e e d b a c k s for the
horizontal, vertical a n d longitudinal plane e a c h , is
e x p e c t e d t o be o p e r a t i o n a l in a u t u m n 2 0 0 2 .
REFERENCES
3500
3000
S y s t e m s o f t w a r e f e a t u r e s , w e did not yet e m p l o y , are
t h e f o l l o w i n g . Filter f u n c t i o n s c a n be set individually for
e a c h D S P calculating t h e kicks for 4 0 b u n c h e s .
S e l e c t i n g a n t i d a m p i n g filter coefficients destabilizing
this s u b s e t of t h e b u n c h p o p u l a t i o n g i v e s an e a s y a n d
for the user n o n d i s t u r b i n g w a y of m e a s u r i n g b e t a t r o n
t u n e s . T r a n s i e n t s of instable b u n c h m o d e s c a n be
m e a s u r e d via a fast s w i t c h i n g of the filter f u n c t i o n s
while measuring.
CONCLUSION
CL
<
A different c a s e is s h o w n in Fig. 5. T h e f e e d b a c k w a s
s w i t c h e d off a n d t h e a m p l i t u d e of t h e resistive wall
instabilities w a s r e d u c e d by a n i n c r e a s e d c h r o m a t i c i t y
setting in the ring optics. W i t h t h e s e r e m o v e d f r o m the
s p e c t r u m , t w o other effects s h o w up. T h e first is a
n a r r o w b a n d c o u p l e d - b u n c h oscillation at f/fo=120.
T h i s is actually not d u e t o a t r a n s v e r s e but to a
longitudinal b e a m oscillation s h o w i n g up slightly the
t r a n s v e r s e s i g n a l . T h e s o u r c e is k n o w n t o be a cavity
higher o r d e r m o d e ( M o d e L9). T h e s e c o n d p e a k is a
wide band resonance spanning several bunch m o d e s
c e n t e r i n g a r o u n d f/fo=20. A s u s p e c t for this c o u l d be a
fast ion instability, w h e r e ions t r a p p e d in t h e ring
c h a m b e r get e x c i t e d by t h e p a s s i n g b e a m .
[1]
D. Bulfone et al., Design
Considerations
ELETTRA
Transverse
Multi-Bunch
PAC'99, N e w Y o r k , M a r c h 1999.
[2]
M. L o n z a et al., Digital Processing
Electronics
for
the ELETTRA
transverse
Multi-Bunch
Feedback
System,
Proc. I C A L E P C S ' 9 9 , T r i e s t e , O c t o b e r
1999.
Cavity HOM
/
1000
500
F i g . 5: C o u p l e d - b u n c h a m p l i t u d e s p e c t r a (1=120 m A ) ,
here with resistive wall instabilities r e d u c e d by high
c h r o m a t i c i t y ( F e e d b a c k off).
for the
Feedback,
39
TOP-UP OPERATION EXPERIENCE
M.
Muñoz
The top-up and frequent filling operation modes have been the standard mode of operation for users at the
SLS for the last year, providing
stable conditions
of operation,
solving limitations
in lifetime due to the
Touscheck
effect and providing better thermal stability. We review the perfomance
of the SLS in this mode.
INTRODUCTION
T h e u s e of f r e q u e n t filling o p e r a t i o n m o d e s is o n e of
the d e s i r e d c h a r a c t e r i s t i c s of m o d e r n s y n c h r o t r o n light
s o u r c e s . T h e S L S is d e s i g n e d to provide a flexible
injection s c h e m e , able t o o p e r a t e in the s o called t o p up a n d f r e q u e n t injection m o d e s . Both m o d e s w e r e
t e s t e d early d u r i n g the c o m m i s s i o n i n g a n d t h e latter
n o w runs routinely as t h e s t a n d a r d m o d e for user
operation, showing a good performance.
Positive f e e d b a c k f r o m S L S u s e r s p r o v e s that c o n t i n u o u s refilling p r o v i d e s excellent c o n d i t i o n s for s y n c h r o t r o n radiation e x p e r i m e n t s , a n d is t h e r e f o r e a n
i m p o r t a n t f e a t u r e of a m o d e r n s y n c h r o t r o n light
source.
T h e u s e of t o p - u p / f r e q u e n t filling s o l v e s s o m e of t h e
p r o b l e m s that m o d e r n S L s o u r c e s h a v e to f a c e :
1.
T o u s c h e c k limited lifetime,
2.
further r e d u c t i o n s o n lifetime d u e t o s m a l l g a p ,
insertion d e v i c e s ,
3.
b e a m stability.
H o w e v e r , t h e u s e of t o p - u p h a s s o m e i m p l i c a t i o n s o n
the d e s i g n of t h e injector s y s t e m , requires g o o d d i a g nostics a n d h a s s o m e effect o n u s e r s e x p e r i m e n t s .
W e review h o w t h e s e p r o b l e m s h a v e b e e n s o l v e d at
the S L S a n d the p e r f o r m a n c e a c h i e v e d in t h e last
year.
—ARI DI-PCT:C U RRE NT I
12:00
12:15
12:30
12:45
13:00
13:15
13:30
13:45
«'f»J.n2tH°
1 4 : 4 5
, s o c
F i g . 1 : C o n t i n u o u s refilling for 3 h o u r s . T h e plot s h o w s
t h e c u r r e n t r e a d i n g for a 3 h o u r s interval.
In both s c e n a r i o s , t h e g a p s of the insertion d e v i c e s
r e m a i n c l o s e d d u r i n g injection a n d t h e s h u t t e r s r e m a i n
open.
A n o t h e r a d v a n t a g e of t o p - u p o p e r a t i o n is t h e inc r e a s e d t h e r m a l stability. T h e c o n s t a n t heat load in the
optical e l e m e n t s i m p r o v e s the p e r f o r m a n c e of the
e x p e r i m e n t s . O n t h e m a c h i n e side, the t h e r m a l
stability r e d u c e s the drift of the different e l e m e n t s ,
t h u s d e c r e a s i n g c l o s e d orbit distortions. A n o t h e r
a d d e d benefit is that c o n s t a n t c u r r e n t o v e r a long t i m e
in the s t o r a g e rings a s s u r e s that the B P M are kept at
c o n s t a n t g a i n , providing m o r e reliable i n f o r m a t i o n .
W H A T IS T O P - U P
T o p - u p c o n s i s t of t h e a l m o s t c o n t i n u o u s r u n n i n g of t h e
injection s y s t e m , in o r d e r to inject a single s h o t in t h e
s t o r a g e ring at periodic intervals in o r d e r t o k e e p a
c o n s t a n t current. T y p i c a l f i g u r e s for t h e c u r r e n t stability are a 0.3 %. For t h e S L S v a l u e s of c u r r e n t a n d
lifetime (12 h at 2 0 0 m A ) , this c o r r e s p o n d s to a n inj e c t i o n at r o u g h l y 2 m i n u t e s interval, whit a n injected
c h a r g e of 0.5 m A .
In o r d e r t o r e d u c e the injection repetition rate, t o d e c r e a s e t h e r e q u i r e d injected c h a r g e a n d not to perturb
t o o m u c h the e x p e r i m e n t at the b e a m l i n e s , a different
a p p r o a c h is to inject e a c h t i m e , the c u r r e n t in t h e ring
r e a c h e s a lower limit, a n d to k e e p the injection r u n n i n g
until it r e a c h e s a n u p p e r limit. T h i s is t h e s o called
f r e q u e n t injection m o d e . A typical o p e r a t i o n m o d e for
the S L S is t o k e e p t h e c h a r g e b e t w e e n 2 0 0 a n d
201 m A , with a n injection cycle e v e r y 5 m i n u t e s , a n d
with d u r a t i o n of t h e injection p r o c e s s b e t w e e n 10 a n d
15 s e c o n d s (see Fig. 1).
TOP-UP AT THE SLS
T h e p l a n n e d u s e of top-tp at S L S h a d i m p o r t a n t
c o n s e q u e n c e s o n t h e d e s i g n of t h e injection c h a i n .
T h e S L S b o o s t e r [1] r e p r e s e n t s a v e r y g o o d s o l u t i o n ,
providing a v e r y low e m i t t a n c e b e a m , with flexible
p o w e r s u p p l i e s a n d excellent low c u r r e n t diagnostic.
T h e p u l s e d m a g n e t s (injection k i c k e r s a n d s e p t u m ) in
t h e s t o r a g e ring are a l s o v e r y a d v a n c e d a n d suited for
top-up operation.
T h e first trials with t o p - u p injection w e r e p e r f o r m e d in
J u n e 2 0 0 1 , a n d s u b s e q u e n t laundry shifts w e r e d o n e
u s i n g it. For user o p e r a t i o n s , it w a s d e c i d e d to s w i t c h
t o f r e q u e n t injection m o d e in t h e m i d d l e of S e p t e m b e r
2 0 0 1 . A f t e r w a r d s , this m o d e h a s b e e n c o n s i d e r e d to
be o n e of the s t a n d a r d m o d e s for user o p e r a t i o n a n d
t h e p r e f e r r e d o n e for s o m e of t h e e x p e r i m e n t s .
T h e c o m b i n a t i o n of the low e m i t t a n c e b e a m c o m i n g
f r o m t h e booster, the w e l l - m a t c h e d t r a n s f e r line a n d
t h e k i c k e r s allow g o o d injection efficiency ( a l m o s t
100 % efficiency c a n be r e a c h e d after o p t i m i s a t i o n
w i t h o u t p r o b l e m s ) . T h i s c a n be r e a c h e d by a c l o s e d
40
injection b u m p that r e d u c e s the d i s t u r b a n c e in the
s t o r e d b e a m , a n d i n c r e a s e s t h e b e a m stability at t h e
s o u r c e point. Fig. 2 s h o w s the position of the s y n c h r o t r o n light s o u r c e at t h e b e a m l i n e 6 S during a t o p up r u n . T h e stability is a s g o o d a s the o n e w i t h o u t t o p up, with no visible effect of t h e injection k i c k e r s .
Beam xtabUUy, M
m
- ?.SS:I, K„ = 11.3:1,
//«-iannídi
¡5/09/01
fSS-í
Position
F i g . 2 : B e a m stability at protein c r y s t a l l o g r a p h y b e a m line 6 S during a t o p - u p r u n .
F i g . 3: T h e plot s h o w s t h e c u r r e n t during a 2 4 h o u r
period in t h e S L S s t o r a g e ring, running c o n t i n u o u s
filling m o d e .
REFERENCES
[1]
W . J o h o , M. M u ñ o z et al., The SLS Booster
chrotron, E P A C 1998.
[2]
L. E m e r y , Top-up at APS. Specifications
and Operating Experience,
p r o c e e d i n g s of " T o p - u p Inj e c t i o n W o r k s h o p " , 9-8 M a r c h , D a r e s b u r y L a b o ratory, UK.
PROBLEMS
T h e t o p - u p o p e r a t i o n at t h e S L S r e q u i r e s certain preconditions. In o r d e r t o h a v e a low f r e q u e n c y of injection, w e m u s t e n s u r e a high injection c h a r g e a n d g o o d
injection efficiency. T h i s requires a stable injection
system.
A n o t h e r point t o c o n s i d e r is the effect of the injection
perturbation o v e r t h e s t o r e d b e a m . In our c a s e , this
effect is s m a l l , but p r o b l e m s in t h e data acquisition at
the e x p e r i m e n t c a n be s o l v e d by gating t h e d e t e c t o r
during the injection, a solution a l r e a d y a d o p t e d at t h e
A P S [2].
CONCLUSION
The SLS
m o d e for
t a n c e by
effect the
drifts.
w a s o p e r a t e d in t o p - u p or f r e q u e n t injection
t h e last six m o n t h , s h o w i n g a g o o d a c c e p the u s e r s . T h i s m o d e h a s a v e r y beneficial
machine performance, reducing the thermal
T h e o p e r a t i o n of S L S in f r e q u e n t injection m o d e h a s
b e e n a s u c c e s s . Fig. 3 s h o w s a typical plot of c u r r e n t
v a l u e s of during a 2 4 hour r u n , with a g o o d c u r r e n t
stability.
Syn-
41
STATUS OF THE SLS CONTROL SYSTEM
S. Hunt, M. Dach, M. Grunder, M. Heiniger,
C. Higgs, M. Janousch,
R. Kappeler,
T.
Korhonen,
R. Krempaska,
J. Krempasky,
A. Luedeke,
D. Maden, T. Pal, W. Portmann,
H.
Pruchova,
D.
Vermeulen
The machine and beamline control system consist of 150 VME crates running Epics on Motorola
Power
PC processors.
The network is based on switched
100 Mbit/sec and Gigabit Ethernet technology.
Consoles and servers are PCs running Linux. To achieve high availability
of the control system, emphasis
has
been put on software engineering
and the use of a relational database for all system configuration.
Most
hardware channels are directly connected
to VME input/output
cards rather than using a field-bus, and this
has resulted in higher performance,
better reliability, and reduced costs. Any of the 100V00 data
channels
can be archived at high speed, and the resulting data accessed
through the Web. The VME
input/output
cards can be 'hot-swapped'
in case of failure, and have circular buffers for post-mortem
analysis in case of
beam loss. Having all machine parameters
available through the control system in a consistent and easy to
use manner has contributed
to the fast and successful
commissioning
of the machine.
CONTROL SYSTEM ARCHITECTURE
E q u i p m e n t interface level
M o n i t o r a n d control of e q u i p m e n t is via t h e direct c o n nection to 150 V M E c r a t e s r u n n i n g E p i c s [1]. S t a n d a r d
I/O m o d u l e s provide interfaces for a n a l o g u e a n d digital input a n d o u t p u t as well a s m o t o r control, t e m perature m e a s u r e m e n t , serial line c o n n e c t i o n , scaler
m o d u l e s a n d position e n c o d e r s . M o s t interfaces are
industry p a c k (IP) m o d u l e s m o u n t e d o n h o t - s w a p V M E
6 4 X carrier b o a r d s . C o n n e c t i o n to signals is on t h e
rear of the crate using 8 0 m m d e e p transition m o d ules.
Network
T h e S L S c o n t r o l s n e t w o r k is a 100 Mbit s w i t c h e d
E t h e r n e t network, with s o m e 1 Gbit c o n n e c t i o n s . T h e
n e t w o r k is isolated, with no routing to t h e rest of the
institute or t o the Internet. S o m e d e v i c e s s u c h as t h e
file a n d d a t a b a s e s e r v e r s are o n both t h e private a n d
g e n e r a l network, allowing t h e e x c h a n g e of data t o
office a n d central s y s t e m s .
Operator interface level
T h e o p e r a t o r interface level c o n s i s t s of Linux P C s
u s e d as c o n s o l e s a n d s e r v e r s . C o n s o l e s in t h e control
r o o m h a v e four s c r e e n s e a c h , a n d a n u m b e r of single
s c r e e n c o n s o l e s , w h i c h a l s o act as boot s e r v e r s , are
located in t h e t e c h n i c a l gallery a n d on b e a m lines.
HIGHLIGHTS
Timing
T h e c o n t r o l s t i m i n g s y s t e m [3] is a high p e r f o r m a n c e
d e s i g n b a s e d on the A P S t i m i n g s y s t e m .
Its high
resolution a n d low jitter p e r f o r m a n c e allows t h e a c c u rate s y n c h r o n i z a t i o n of h a r d w a r e signals a n d s o f t w a r e
a c r o s s t h e S L S control s y s t e m . Its u s e simplifies the
o p e r a t i o n of t h e m a c h i n e allowing c o m p l e x s e q u e n c e s
of e v e n t s to be c a r r i e d out by c h a n g i n g v e r y f e w par a m e t e r s . Its integration into E p i c s m e a n s t i m i n g par a m e t e r s c a n be t r e a t e d j u s t like a n y o t h e r control
s y s t e m variable.
Online model server
T h e on-line m o d e l server a n d p h y s i c s a p p l i c a t i o n s are
p r o v i d e d by t h e b e a m d y n a m i c s g r o u p [4]. T h e m o d e l
server c a n read the b e a m positions a n d actual m a g n e t
s t r e n g t h s f o r m the control s y s t e m a n d c a n v e r y
a c c u r a t e l y predict the effects of p r o p o s e d n e w settings
before t h e y are i m p l e m e n t e d . T h e v e r y
close
a g r e e m e n t of t h e m o d e l a n d m a c h i n e m a k e it possible
t o a c h i e v e v e r y g o o d m a c h i n e p e r f o r m a n c e including
b e a m stability.
Integration of Beamlines
B e a m l i n e c o n t r o l s [5] are h a n d l e d by t h e s a m e h a r d w a r e a n d s o f t w a r e u s e d for m a c h i n e c o n t r o l s . A s well
a s r e d u c i n g c o s t s a n d d e v e l o p m e n t t i m e this h a s e n a b l e d c o n t r o l s e n g i n e e r s to w o r k o n either s y s t e m a s
priorities dictate
Integration of sub-systems with turn-key controls
Both, the Linac a n d t h e R F m o d u l a t o r s y s t e m s w e r e
delivered by industry a s turn k e y c o n t r a c t s [2]. T h e s e
s y s t e m s w e r e delivered with an E p i c s control s y s t e m
m a k i n g it s i m p l e t o integrate into t h e global control
system.
Moving physics applications and parameters into
the control system
Calculation of s o m e m a c h i n e p a r a m e t e r s h a s b e e n
m o v e d f r o m high-level a p p l i c a t i o n s into the low-level
control s y s t e m [6]. T h i s p r o v i d e s m o r e stability a n d
higher p e r f o r m a n c e . It a l s o allows t h e u s e of our s t a n d a r d tools s u c h as t h e archiver, a l a r m h a n d l e r a n d
s a v e - r e s t o r e tools.
Digital p o w e r s u p p l y control
Control of t h e 5 0 0 b o o s t e r a n d s t o r a g e ring m a g n e t s is
c a r r i e d out using individual fully digital p o w e r s u p p l i e s .
T h i s h a s c o n t r i b u t e d t o t h e v e r y high stability of the
e l e c t r o n b e a m . Interface to the V M E c r a t e s f r o m the
p o w e r s u p p l y controller is via a c u s t o m d e s i g n e d
optical serial link. All internal control p a r a m e t e r s a n d
42
r e a d i n g s c a n be read a n d set via this link a n d a p p e a r
as s t a n d a r d Epics p r o c e s s v a r i a b l e s .
Hot s w a p and post m o r t e m analysis
M o s t of o u r I/O m o d u l e s s u p p o r t t h e f e a t u r e s of hot
s w a p a n d h a v e h a r d w a r e buffers for p o s t - m o r t e m
analysis following loss of b e a m or o t h e r e v e n t s . T h e
a n a l o g u e input m o d u l e s a l s o s u p p o r t o v e r - s a m p l i n g of
data t o give 18-bit resolution a n d noise r e d u c t i o n by
averaging.
Relational database
A n O r a c l e relational d a t a b a s e is u s e d for s y s t e m c o n figuration, a n d o p e r a t i o n a l m a n a g e m e n t . F e a t u r e s
p r o v i d e d include g e n e r a t i n g c o n f i g u r a t i o n files (Archiving, C d e v , etc.), reporting of b u g s a n d s y s t e m
failures, t r a c k i n g the location of all h a r d w a r e m o d u l e s ,
a n d g e n e r a t i n g E p i c s substitution files. U s e r s interrogate a n d m o d i f y d a t a b a s e t a b l e s using a W e b interface.
REASONS FOR SUCCESS
Standardization
W e h a v e s u c c e e d e d in s t a n d a r d i z i n g o n a s m a l l n u m ber of different h a r d w a r e m o d u l e s . T h e s a m e h a r d w a r e is u s e d t o m o n i t o r a n d control a large variety of
devices. This has reduced development time and
m a k e s m a i n t e n a n c e easier. T h e s a m e v e r s i o n of
s o f t w a r e is l o a d e d into all s y s t e m s a n d regularly
a u t o m a t i c a l l y u p d a t e d . T h i s includes low-level softw a r e (Epics s y s t e m c o d e a n d drivers), a s well a s
s y s t e m c o d e , application c o d e , a n d c o n f i g u r a t i o n files
on Linux s e r v e r s a n d w o r k s t a t i o n s . W h e n a d e v e l o p e r
c h a n g e s an application on r e q u e s t t h e c h a n g e s are
distributed t o all s y s t e m s .
Not b u i l d i n g h a r d w a r e in h o u s e
W h e r e possible, c o m m e r c i a l off the shelf m o d u l e s
h a v e b e e n u s e d . W h e r e s u c h m o d u l e s w e r e not available to m e e t o u r r e q u i r e m e n t s , c o n t r a c t s w e r e p l a c e d
with industry for d e s i g n a n d p r o d u c t i o n of t h e n e c e s s a r y m o d u l e s . C o n t r a c t s for d e s i g n a n d p r o d u c t i o n of
V M E a n d industry p a c k m o d u l e s n o w include the provision of Epics drivers. T h i s h a s further r e d u c e d t h e
t i m e for testing a n d integration into t h e control s y s t e m .
No Fieldbus
By h a v i n g direct c o n n e c t i o n using V M E I/O rather t h a n
using a fieldbus level, the s y s t e m is simpler, m o r e
robust a n d h a s higher p e r f o r m a n c e . C o s t per c h a n n e l
is low d u e to high signal densities, a n d m a i n t e n a n c e
a n d d e b u g g i n g are easier.
Not making major software developments
By largely using existing s o f t w a r e c o m p o n e n t s , w e
h a v e b e e n able t o c o n c e n t r a t e on solving t h e c o n t r o l s
p r o b l e m s n e e d e d for e a c h s u b s y s t e m . T h i s h a s
m e a n t w e w e r e able t o deliver w o r k i n g c o n t r o l s s y s t e m s early in t h e project, a n d did not e x p e r i e n c e any
m a j o r p r o b l e m s bringing t h e s y s t e m into o p e r a t i o n .
E v e n w h e n s o m e t o o l s did not provide all of t h e f e a t u r e s w e w o u l d h a v e ideally liked, w e h a v e lived with a
slightly r e d u c e d functionality, rather that e m b a r k o n
major developments.
REFERENCES
[1]
L. Dalesio et al., The Experimental
Physics
Industrial
Control System Architecture:
Past,
sent and Futur, I C A L E P C S 1993, Berlin.
and
Pre-
[2] S. Hunt, Purchasing
Accelerator
Subsystems
Turnkey
Components,
ICALEPCS 2001,
Jose.
as
San
[3] T. K o r h o n e n , M. Heiniger, Timing System of the
Swiss Light Source, I C A L E P C S 2 0 0 1 , S a n J o s e .
[4]
M. B ö g e , J . C h r i n , On the use
Level
Software
Applications
ICALEPCS 2001, San Jose.
of Corba in
at
the
High
SLS,
[5] J . K r e m p a s k y et al., The SLS Beamlines
Data
Acquisition
and Control System , I C A L E P C S 2 0 0 1 ,
San Jose.
[6] A. L u e d e k e , System integration
of high level
cations during commissioning
of the Swiss
Source, I C A L E P C S 2 0 0 1 , S a n J o s e .
appliLight
43
BEAMLINES, OVERVIEW
44
BEAMLINES AND USER ASPECTS
J.F. van der Veen,
STATUS OF THE BEAMLINES
T h e important target of " p h o t o n s o n s a m p l e " at t h e
S L S by A u g u s t 2 0 0 1 c o u l d be met, t h a n k s t o t h e d e d i c a t e d i n v o l v e m e n t of the S L S c r e w a n d o u r coll e a g u e s within P S I . T h e c o l l a b o r a t i o n s w i t h B E S S Y ,
S P R I N G - 8 , E L E T T R A a n d A P S , as well as with coll e a g u e s f r o m S w i s s universities a n d E T H greatly c o n tributed t o t h e s u c c e s s .
M i l e s t o n e s in 2 0 0 1 :
•
T h e insertion d e v i c e s W 6 1 (wiggler), U 2 4 (inv a c u u m u n d u l a t o r ) , o n e unit of U E 5 6 ( S a s a k i / A P P L E - l l t y p e u n d u l a t o r ) a n d t h e t w o units
of U E 2 1 2 ( e l e c t r o m a g n e t i c u n d u l a t o r ) h a v e b e e n
installed in t h e s t o r a g e ring. T h e influence of t h e
insertion d e v i c e s o n t h e e l e c t r o n orbit h a s b e e n
studied and minimized.
•
T h e optics of the m a t e r i a l s s c i e n c e ( M S ) b e a m line h a s b e e n c o m m i s s i o n e d a n d the t o m o g r a p h y
a n d p o w d e r diffraction stations are n o w in
o p e r a t i o n . T h e s u r f a c e d i f f r a c t o m e t e r will be
installed in J a n u a r y 2 0 0 2 . T h e large heat load
g e n e r a t e d by t h e w i g g l e r at a g a p of 11.5 m m is
h a n d l e d by a rotating c a r b o n filter. In 2 0 0 2 , t h e
w i g g l e r g a p will be r e d u c e d further.
•
First b e a m o n the protein c r y s t a l l o g r a p h y ( P X )
b e a m l i n e w a s d e t e c t e d in M a y 2 0 0 1 . T h e
c o m m i s s i o n i n g of t h e o p t i c s t o o k place in J u n e
a n d July, a n d t h e first h i g h - r e s o l u t i o n d a t a w e r e
collected o n J u l y 12. T h e i n - v a c u u m undulator,
on loan f r o m S P R I N G - 8 , p e r f o r m s well a n d h a s
b e e n o p e r a t e d w i t h o u t r e d u c t i o n of b e a m lifetime
at g a p s d o w n t o 6.5 m m . A total of 7 0 user shifts
w a s d e l i v e r e d t o 14 different g r o u p s , 6 of t h e m
f r o m industry.
•
At the b e a m l i n e for s u r f a c e a n d interface s p e c t r o s c o p y (SIS), t h e u n d u l a t o r a n d the e l e c t r o n
energy analyser have been commissioned and
the first p h o t o e m i s s i o n d a t a h a v e b e e n t a k e n .
O p e r a t i o n of the U E 2 1 2 in t h e a p e r i o d i c m o d e led
to a s u b s t a n t i a l r e d u c t i o n of higher h a r m o n i c s in
the p h o t o e m i s s i o n s p e c t r a . T h i s allows for
d e t a i l e d s t u d i e s of the F e r m i - e d g e of m a t e r i a l s ,
essentially free of b a c k g r o u n d .
•
T h e b e a m l i n e for s u r f a c e a n d interface m i c r o s c o p y ( S I M ) r e c e i v e d the u n d u l a t o r U E 5 6 in
November
2001.
Despite
the
late
start,
substantial
progress
was
made
with
the
c o m m i s s i o n i n g of the optics. T h e first flux c u r v e s
were
measured.
Earlier
in t h e
year,
the
photoemission microscope was commissioned.
S o o n , t h e first pilot e x p e r i m e n t s will t a k e p l a c e .
R.
Abela
•
First m e a s u r e m e n t s w e r e m a d e with t h e pixel
and
microstrip
detectors. The
point-spread
f u n c t i o n of the pixel d e t e c t o r is excellent. First
priority n o w is r e d u c i n g t h e p e r c e n t a g e of d e a d
pixels. T h e microstrip d e t e c t o r w a s e m p l o y e d t o
r e c o r d p o w d e r diffraction data a s a f u n c t i o n of
time.
•
T h e t o p - u p m o d e of m a c h i n e o p e r a t i o n w a s u s e d
succesfully and
is b e c o m i n g the
favourite
o p e r a t i o n m o d e for user runs.
F i g . 1 : B e a m l i n e layout at t h e S L S
PLANNING OF NEW BEAMLINES AND STATIONS
S u b s t a n t i a l p r o g r e s s w a s m a d e in t h e p l a n n i n g a n d
d e s i g n of n e w b e a m l i n e s :
•
T h e optical layout of the u n d u l a t o r b e a m l i n e for
m i c r o - X A F S h a s b e e n m a d e a n d t h e d e s i g n report h a s b e e n c o m p l e t e d at t h e e n d of t h e year.
•
A start h a s b e e n m a d e with t h e F E M T O - p r o j e c t ,
a i m e d at realising f e m t o s e c o n d p u l s e s u s i n g
e l e c t r o n - b e a m slicing t e c h n i q u e s . T h e m a c h i n e
group has studied how the electron b e a m properties w o u l d b e affected by t h e p l a c e m e n t of t h e
m o d u l a t o r , radiator a n d t h e d i s p e r s i v e s e c t i o n in
a single long straight s e c t i o n . F r o m the point of
v i e w of e l e c t r o n b e a m optics, t h e r e s e e m to be
no m a j o r o b s t a c l e s . E x t r e m e l y c h a l l e n g i n g will b e
the s e p a r a t i o n of t h e s l i c e d b e a m f r o m t h e m a i n
beam.
•
P r e p a r a t i o n s for a c o l l a b o r a t i o n with c o l l e a g u e s
from LURE and SOLEIL have been made. This
involves t h e realisation of a n u n d u l a t o r b e a m l i n e
at S L S for m i c r o - X A F S e x p e r i m e n t s in t h e soft X ray r e g i o n . T h i s d e m a n d i n g e n e r g y r e g i m e
includes the a b s o r p t i o n e d g e s of a n u m b e r of
environmentally important elements.
45
•
A b e n d i n g m a g n e t b e a m l i n e will be d e v o t e d to
m a c h i n e d i a g n o s t i c s a n d for t e s t s of optical
c o m p o n e n t s . T h e b e a m l i n e will be r e a l i s e d in
2002.
•
A t t h e e n d of 2 0 0 1 , a start w a s m a d e with t h e
t e c h n i c a l layout of a b e n d i n g - m a g n e t b e a m l i n e
for infrared s p e c t r o s c o p y , at a later s t a g e t o b e
c o m b i n e d with V U V - s p e c t r o s c o p y .
T h e f o l l o w i n g n e w s t a t i o n s are p l a n n e d :
•
•
A t t h e S I M b e a m l i n e , a station for soft X - r a y
r e s o n a n t s c a t t e r i n g s t u d i e s of m a g n e t i s m a n d
c o r r e l a t e d - e l e c t r o n s y s t e m s (in c o l l a b o r a t i o n with
colleagues from CNRS, Grenoble).
B e l o w are s o m e user statistics (status O c t o b e r 2 0 0 1 ).
Distribution of user groups over disciplines
Life sciences
Materials science
Environmental sciences
Chemistry, energy research
Surface science
0
5
10
15
20
25
30
Nr. of groups
A t a s i d e b r a n c h of t h e S I S b e a m l i n e , a station
for X - r a y interference lithography. T h i s activity is
led by the L a b o r a t o r y for Micro- a n d N a n o t e c h n o l o g y ( L M N ) at P S I .
USER ASPECTS
In 2 0 0 1 , v a r i o u s specialist user g r o u p s c o n v e n e d at
S L S . T h e g e n e r a l u s e r s m e e t i n g , held o n N o v e m b e r
14 a n d 15, w a s a t t e n d e d by m o r e t h a n 100 p e r s o n s .
Furthermore:
•
T h e S L S w a s officially i n a u g u r a t e d on 19 O c t o ber 2 0 0 1 , in t h e p r e s e n c e of Federal Councillor
Ruth D r e i f u s s .
•
A proposal review committee has been formed,
chair Prof. W . D . S c h n e i d e r (Univ. L a u s a n n e ) .
•
A call for p r o p o s a l s for pilot e x p e r i m e n t s w a s
s e n t out in Juni 2 0 0 1 to e x p e r t u s e r s . A b o u t 4 0
p r o p o s a l s w e r e s u b m i t t e d , of w h i c h a n u m b e r rec e i v e d b e a m t i m e o n the M S a n d P X b e a m l i n e s .
•
A f o r m a l call for p r o p o s a l s w a s s e n t t o E u r o p e a n
s c i e n c e m a g a z i n e s for p u b l i c a t i o n . T h e call a p p e a r s in J a n u a r - F e b r u a r y 2 0 0 2 . D e a d l i n e for a p plication is 8 M a r c h 2 0 0 2 .
•
A n u m b e r of p h a r m a c e u t i c a l c o m p a n i e s h a v e
u s e d o u r P X b e a m l i n e . C o n t r a c t s for proprietary
u s e in 2 0 0 2 h a v e b e e n s i g n e d .
Geographical distribution of SLS user groups
EUrB
'rAci^taen
(3»
pg
tm
<9
m
F i g . 2 : Statistics of (potential) u s e r s of S L S
46
47
BEAMLINES, DETAILS
48
SURFACE / INTERFACE SPECTROSCOPY BEAMLINE
L. Patthey,
M. Shi,
J. Krempasky,
T. Schmidt,
R.
U. Flechsig,
Abela
C. Quitmann,
R. Betemps,
M.
Botkine,
In this contribution
we report on the status of the Surface and Interface Spectroscopy
beamline (SIS), which is
under commissioning
at the SLS. This beamline
is allows studies of the electronic
and atomic structure
of
surfaces
and interfaces
over a wide temperature
range. The twin undulator
UE212 and the optics of the
beamline are operational
and provide light with high-energy
resolution
and with low higher-harmonic
content.
The first measurements
have been performed
with the photoelectron
spectrometer.
Using the
quasiperiodic
scheme
of the UE212
the strong
rejection
of higher
harmonic
radiation
required
for
high-resolution
photoemission
experiment
was achieved.
T h e S u r f a c e a n d Interface S p e c t r o s c o p y b e a m l i n e
(SIS) p r o v i d e s a state-of-the-art e x p e r i m e n t a l set-up
to s t u d y t h e electronic a n d a t o m i c structure of surf a c e s . T h e b e a m l i n e h a s b e e n d e s i g n e d for high
p h o t o n e n e r g y resolution with low h a r m o n i c c o n t a m i nation a n d v a r i a b l e light polarization. T h e r e f o r e , this
b e a m l i n e is well suited for h i g h - r e s o l u t i o n p h o t o e m i s s i o n , a n g l e - r e s o l v e d ultra-violet p h o t o e l e c t r o n s p e c t r o s c o p y ( A R U P S ) , p h o t o e l e c t r o n diffraction, F e r m i
surface mapping, X-ray absorption spectroscopy
( X A S ) a n d X - r a y e m i s s i o n s p e c t r o s c o p y ( X E S ) exp e r i m e n t s . T h e p h o t o n e n e r g y r a n g e is 1 0 - 8 0 0 e V
with a n overall resolving p o w e r E/AE > 1 0 0 0 0 . T h e
b e a m l i n e is d e s c r i b e d in m o r e detail in r e f e r e n c e s [ 1 2].
EXPERIMENTAL STATION
T h e e x p e r i m e n t a l station (Fig. 1) h a s b e e n d e l i v e r e d
a n d installed at PSI in t h e spring of 2 0 0 1 by P I N K
V a c u u m , G e r m a n y . T h e e x p e r i m e n t a l station is
e q u i p p e d with a h i g h - r e s o l u t i o n p h o t o e l e c t r o n s p e c t r o m e t e r S E S - 2 0 0 2 f r o m G a m m a d a t a with a d e m o n strated resolution of 1.7 m e V [3]. A precision m a n i p u lator e q u i p p e d with a H e - f l o w cryostat f r o m low t e m perature facilities g r o u p at PSI [4] a n d a high
precision s a m p l e rotation s t a g e [5] is m o u n t e d o n the
e x p e r i m e n t a l station. T h i s m a n i p u l a t o r a l l o w s for
a n g l e - r e s o l v e d m e a s u r e m e n t s o v e r 2n s t e r a d i a n
d o w n t o 10 K. At present, t h e a c h i e v e d resolution o n
solid s a m p l e s is 8.6 m e V (Fig. 2), t h e s p e c t r u m is
r e c o r d e d with H e l a radiation. T h e X A S s p e c t r o m e t e r
will be installed in m i d d l e 2 0 0 2 w h i l e t h e X E S
s p e c t r o m e t e r is s c h e d u l e d for e n d 2 0 0 2 .
F i g . 1 : S i d e v i e w of t h e e x p e r i m e n t a l station installed
on t h e large rotating p l a t f o r m .
'
^
=i
'
~
S
>>
'
-\
'
\
'
'
'
•
Cu (110) Fermi edge
hv-21.2eV
T " 10.5 K
B i n d i n g Energy ( m e V )
Fig. 2: Fermi edge photoemission
C u ( 1 1 0 ) at low t e m p e r a t u r e .
spectrum
from
BEAMLINE OPTICS
T h e m o n o c h r o m a t o r [2] of t h e b e a m l i n e c o m b i n e s
normal-incidence (NIM) and grazing-incidence (PGM)
g r a t i n g s a n d o p e r a t e s with vertically a n d horizontally
collimated beam. The monochromator
(Jenoptik,
G e r m a n y ) , t h e mirror c h a m b e r s (Bestec, G e r m a n y ) ,
g r a t i n g s , a n d t h e m i r r o r s (Carl Z e i s s , G e r m a n y ) w e r e
d e l i v e r e d in D e c e m b e r 2 0 0 0 . Until e n d of J u l y 2 0 0 1 ,
49
all
optical
components
were
installed.
The
c o m m i s s i o n i n g of t h e S I S b e a m l i n e started in A u g u s t
2 0 0 1 . Fig. 3 s h o w s t h e s p e c t r u m of t h e U E 2 1 2
u n d u l a t o r m e a s u r e d b y a n e n e r g y s c a n of t h e
monochromator. T h e fundamental and the harmonics
up t o t h e 9
o r d e r a r e clearly visible. F o r this
measurement the monochromator was scanned from
h v = 2 0 e V u p t o 1 2 6 e V with a fixed f o c u s c o n s t a n t of
Cff = 2 . 0 . T h e u n d u l a t o r U E 2 1 2 w a s o p e r a t e d at a
c o n s t a n t c u r r e n t I = 7 0 A l e a d i n g t o a f u n d a m e n t a l at
hv = 2 3 . 5 e V . T h e p e a k s in t h e figure a r e labeled b y
the u n d u l a t o r h a r m o n i c a n d t h e grating diffraction
order.
t h
h a r m o n i c signal is s u p p r e s s e d b y a f a c t o r of m o r e
t h a n 1 2 5 (for t h e 3 r d h a r m o n i c ) a n d t h e b a c k g r o u n d
at E is r e d u c e d b y a f a c t o r of 3 5 . U s i n g t h e q u a s i periodic m o d e results in a p h o t o n b e a m of high
spectral purity with less t h a n 0.5 % h i g h e r h a r m o n i c
contamination.
F
Ag4d
fundamental
(hv-23.2 eV)
U 2 1 2 energy scan
U2l2curren1:70A
Ag 4dfromhigher harminc light:
ring c u r r e n t : 1 6 m A
2nd. harmonic
(hv-46.4 eV)
a p e r t u r e : (D.3 x 1.5) m
Ctl: 2.0
3rd. harmonic
(hv-69.6 eV)
g r a t i n g : 30O.'mm
A.
/
—I
-10
1
1
-20
-30
Binding Energy (eV)
I—
-50
Fig. 4 : P h o t o e m i s s i o n s p e c t r u m r e c o r d e d with t h e
U E 2 1 2 o p e r a t i n g in n o r m a l - (blue) a n d q u a s i p e r i o d i c m o d e (red).
photon energy OV)
REFERCENCES
Fig. 3 : E n e r g y s c a n of t h e m o n o c h r o m a t o r s h o w i n g
the s p e c t r u m of the U E 2 1 2 undulator.
[1]
L. Patthey,
T. Schmidt,
U. F l e c h s i g ,
C. Q u i t m a n n , M. S h i , R. B e t e m p s , M. B o t k i n e ,
R. A b e l a ,
Surface
and
Interface:
SPECTROSCOPY
beamline,
P S I Scientific
Report 2 0 0 0 , V o l u m e V I I , 6 0 .
[2]
U. F l e c h s i g ,
L. Patthey,
C. Q u i t m a n n ,
Plane
Grating Monochromators
for the SLS soft x-ray
beamlines,
P S I Scientific Report 2 0 0 0 , V o l u m e
VII, 62.
[3]
T e s t e d with g a s cell a n d m o n o c h r o m a t i z e d H e plasma UV source from Gammadata Scienta.
[4]
P. Boni, B. v a n d e n Brandt, P. Hautle, J.A. K o n ter, S . M a n g o , M. Zolliker, A compact
helium
flow cryostat
for TASP, P S I Scientific R e p o r t
1 9 9 8 , V o l u m e III, 7 3 .
[5]
P. A e b i , private
[6]
T . S c h m i d t , G . Ingold, A . Imhof, B.D. P a t t e r s o n ,
L. Patthey,
C. Q u i t m a n n ,
C. S c h u l z e - B r i e s e ,
R. A b e l a , N u c l . Inst, a n d M e t h . A 4 6 7 - 4 6 8
(2001) 126-129.
INSERTION DEVICE
T h e twin U E 2 1 2 u n d u l a t o r c o n s i s t of t w o e l e c t r o m a g net u n d u l a t o r s [6] m a n u f a c t u r e d b y B u d k e r Institute
of N u c l e a r P h y s i c s in N o v o s i b i r s k , R u s s i a . T h e t w o
u n d u l a t o r s w e r e installed in t h e S L S t u n n e l in J u n e
2 0 0 1 a n d in O c t o b e r 2 0 0 1 , respectively. T h e y a r e
both in o p e r a t i o n . T h e q u a s i p e r i o d i c m o d e w a s t e s t e d
for t h e first t i m e in O c t o b e r 2 0 0 1 . In this m o d e , t w o
separate power supplies are used to power the
U E 2 1 2 , a c u r r e n t of U = 6 0 A a n d l = 7 2 A,
respectively. T h i s setting p r o v i d e s a n a m p l i t u d e
m o d u l a t i o n of t h e m a g n e t i c field o p t i m i z e d t o r e d u c e
the overall h a r m o n i c c o n t a m i n a t i o n . T h e h a r m o n i c
contamination
was
measured
using
the
p h o t o e m i s s i o n signal of 4 d state of a solid silver
s a m p l e a n d is s h o w n in Fig. 4 . T h e signal a b o v e t h e
F e r m i e n e r g y ( E ) is entirely d u e t o h i g h e r - o r d e r light
e m i t t e d b y t h e undulator. In t h e periodic m o d e (blue)
the light f r o m higher h a r m o n i c s g i v e s a n u n d e s i r a b l e
4 d s i g n a l a b o v e E a n d a n important b a c k g r o u n d at
E . W i t h t h e q u a s i p e r i o d i c m o d e (red), t h e h i g h e r
2
F
F
F
communication.
50
SURFACE / INTERFACE MICROSCOPY BEAMLINE
C. Quitmann,
U. Flechsig,
G. Ingold,
R. Krempaska,
J. Krempasky,
F. Nolting,
L. Patthey,
T.
Schmidt
All major components
of the Surface/Interface
Microscopy
(SIM) beamline have been installed and commissioning
has started successfully.
The photoemission
electron microscope
(PEEM) has delivered
first
images. The optics and the undulator
were installed
and first undulator
light was successfully
guided
through the entire beamline allowing preliminary
checks of the different
components.
INTRODUCTION
T h e S u r f a c e / I n t e r f a c e : M i c r o s c o p y ( S I M ) B e a m l i n e will
a l l o w t o s t u d y t h e electronic a n d g e o m e t r i c structure
of s u r f a c e s o n a n a n o m e t e r s c a l e [ 1 ] . B e c a u s e of t h e
large flexibility in the light polarization it is particularly
well suited for dichroic e x p e r i m e n t s o n m a g n e t i c s a m ples. T h e m a i n d e s i g n p a r a m e t e r s are g i v e n in
T a b l e 1.
Photon energy
95 - 2 0 0 0 e V
Photon energy resolution
hv / A h v > 5 0 0 0
Polarization
Linear: (-6° t o 186°)
Circular: right or left
Spatial resolution
30 - 1 0 0 nm
Photoelectron energy
resolution
0.15 e V
Sample temperature
120 K < T < 1 8 0 0 K
D u r i n g t h e first c o m m i s s i o n i n g period t h e e n e r g y a n a lyzer is not installed t o r e d u c e t h e c o m p l e x i t y of t h e
i n s t r u m e n t . It will be a d d e d in 2 0 0 2 .
Optics
T h e optical layout is b a s e d on a p l a n e g r a t i n g m o n o c h r o m a t o r with c o l l i m a t e d light [ 2 ] . T h e quality of t h e
mirrors a n d g r a t i n g s w a s t e s t e d in c o l l a b o r a t i o n with
t h e m e t r o l o g y l a b o r a t o r i e s at E L E T T R A a n d E S R F . All
optical c o m p o n e n t s m e t or e x c e e d e d t h e s p e c i f i c a tions. By S e p t e m b e r 2 0 0 1 , the m e c h a n i c s a n d optics
w e r e installed, a l i g n e d , a n d r e a d y for c o m m i s s i o n i n g .
Fig. 2 s h o w s a n inside v i e w of t h e radiation s h i e l d e d
Pb-hutch.
T a b l e 1 : D e s i g n p a r a m e t e r s of S I M b e a m l i n e a n d t h e
PEEM microscope.
STATUS
Microscope
T h e m i c r o s c o p e (Fig. 1) w a s d e l i v e r e d in M a r c h by
ELMITEC
Elektronenmikroskopie
GmbH. It w a s installed a n d within 3 d a y s d e l i v e r e d first i m a g e s .
F i g . 2 : Inside v i e w of the P b - h u t c h s h o w i n g t h e collim a t i n g mirror c h a m b e r , the p r i m a r y radiation s h i e l d ,
an a p e r t u r e unit, a n d t h e m o n o c h r o m a t o r (left to right).
All m a j o r c o m p o n e n t s are installed a n d first tests w e r e
successful.
Insertion device
T h e t w o u n d u l a t o r s U E 5 6 are b e i n g built in c o l l a b o r a tion with B E S S Y [ 3 ] . U s i n g t w i n u n d u l a t o r s will a l l o w
rapid helicity s w i t c h i n g [ 1 ] . T h e first d e v i c e w a s c o m pleted in O c t o b e r 2 0 0 1 a n d w a s installed d u r i n g t h e
N o v e m b e r s h u t - d o w n . It is s h o w n in Fig. 3. T h e p h a s e
error is b e l o w 3° a l l o w i n g o p e r a t i o n o n t h e h i g h e r u n dulator h a r m o n i c s w i t h o u t significant loss of intensity.
T h e s e c o n d d e v i c e is b e i n g a s s e m b l e d a n d will be
installed in m i d 2 0 0 2 .
F i g . 1 : T o p v i e w of t h e S I M e n d s t a t i o n s h o w i n g t h e
P E E M a n d t h e a s s o c i a t e d r a c k s for e l e c t r o n i c s . T h e
light e n t e r s t h e m i c r o s c o p e f r o m the right h a n d s i d e .
51
C o m m i s s i o n i n g will c o n t i n u e in F e b r u a r y 2 0 0 2 after
u p g r a d i n g t h e c o o l i n g s y s t e m of t h e optics a n d after
t h e installation of a s e c o n d g r a t i n g ( 1 2 0 0 / m m ) . T e s t s
of the twin u n d u l a t o r c o n c e p t for helicity s w i t c h i n g
[ 1 , 3] will b e p e r f o r m e d after installation of the s e c o n d
U E 5 6 in the s u m m e r .
P L A N S FOR 2002/2003
Beamline
After c o m p l e t i n g t h e c o m m i s s i o n i n g w o r k v a r i o u s upg r a d e s will be installed. T h e s e include a s e p a r a t e
p r e p a r a t i o n c h a m b e r for s a m p l e p r e p a r a t i o n in U H V
a n d i m p r o v e d r e f o c u s o p t i c s u s i n g b e n d a b l e mirrors.
User operation
F i g . 3: U n d u l a t o r U E 5 6 / I prior to its installation. A
s e c o n d identical d e v i c e is b e i n g a s s e m b l e d . T h e t w i n
u n d u l a t o r s will a l l o w rapid helicity s w i t c h i n g .
Commissioning results
T h e s h o r t t i m e b e t w e e n t h e u n d u l a t o r installation a n d
the Christmas s h u t - d o w n w a s u s e d for a first c o m m i s s i o n i n g p e r i o d . Light w a s g u i d e d t h r o u g h t h e b e a m l i n e
a n d first p r e l i m i n a r y t e s t s w e r e p e r f o r m e d . A first flux
c u r v e m e a s u r e d using a S i - d i o d e b e h i n d t h e r e f o c u s
mirror is s h o w n in Fig. 4 . For a m a g n e t i c g a p of
18.0 m m , the f u n d a m e n t a l of the u n d u l a t o r is l o c a t e d
at hv = 113.8 e V . T h i s p h o t o n e n e r g y a n d t h e w i d t h of
3 % F W H M a s well a s the s i d e - b a n d s w h i c h are visible in this l o g a r i t h m i c plot a g r e e well with t h e c a l c u lated p e r f o r m a n c e of t h e U E 5 6 ( 3 2 p e r i o d s ) . S m a l l
a m o u n t s of higher o r d e r light are visible at h i g h e r
photon energy.
F i g . 4 : First flux c u r v e m e a s u r e d after the r e f o c u s
mirror at t h e S I M b e a m l i n e with a single u n d u l a t o r a n d
3 0 m A ring current. A s i d e f r o m the f u n d a m e n t a l at
113.8 e V , h i g h e r o r d e r radiation is visible at 143 e V
a n d 151 e V . U n d u l a t o r s i d e - b a n d s c a n be s e e n o n
both s i d e s of t h e f u n d a m e n t a l .
After finishing t h e basic c o m m i s s i o n i n g w o r k t h e
b e a m l i n e will be t e s t e d in c o o p e r a t i o n with u s e r s during a set of pilot e x p e r i m e n t s . In t h e s e c o n d half of
2 0 0 2 t h e first regular u s e r s will be able t o p e r f o r m
e x p e r i m e n t s at this b e a m l i n e .
REFERENCES
[1]
C. Q u i t m a n n , U. F l e c h s i g , L. Patthey, T. S c h m i d t ,
G. Ingold, M. H o w e l l s , M. J a n o u s c h , R. A b e l a ,
Surface Science 480 (2001) 173-179.
[2]
U. F l e c h s i g , L. Patthey, C. Q u i t m a n n , N u c l . Instr.
Meth. A 467-468 (2001 ) 4 7 9 - 4 8 1 .
[3]
T. S c h m i d t , G. Ingold, A. Imhof, B.D. P a t t e r s o n ,
L. Patthey,
C. Q u i t m a n n ,
C. S c h u l z e - B r i e s e ,
R. A b e l a , N u c l . Instr. M e t h . A 4 6 7 - 4 6 8 ( 2 0 0 1 )
126-129.
52
THE MATERIALS SCIENCE BEAMLINE
B.D. Patterson,
Th. Bortolamedi,
The Materials Science
test user
operation.
Beamline
Q. Chen,
F. Gozzo, M. Kropf,
P.R.
Willmott
M. Lange,
saw "first light" in 2001 and is presently
INTRODUCTION
T h e Materials S c i e n c e B e a m l i n e [1] at t h e S w i s s
Light S o u r c e is d e s i g n e d to provide a high flux of
hard X - r a y s (5-40 k e V ) into a s m a l l s p o t ( 1 x 1 m m )
at o n e
of t h r e e
experimental
stations:
X-ray
T o m o g r a p h i c M i c r o s c o p y ( X T M - 32 m f r o m t h e
s o u r c e ) , P o w d e r Diffraction ( P D - 36 m ) a n d S u r f a c e
Diffraction ( S D - 4 1 m ) . Fig. 1 p r e s e n t s a s c h e m a t i c
plan of t h e b e a m l i n e optics, s h o w i n g ( f r o m left to
right): t h e w i g g l e r s o u r c e point, t h e first (verticallyc o l l i m a t i n g ) mirror, the first m o n o c h r o m a t o r crystal,
the s e c o n d (horizontally-focusing) m o n o c h r o m a t o r
crystal, t h e s e c o n d (vertically-focusing) mirror a n d t h e
f o c u s point (at o n e of the t h r e e e x p e r i m e n t a l
stations).
2
F i g . 1 : S c h e m a t i c plan of the b e a m l i n e optics.
D. Maden,
undergoing
B.
Schmitt,
commissioning
and
"first light". T h i s n o n - o p t i m i z e d
bending-magnet
radiation w a s t h e n u s e d t o c h e c k the a l i g n m e n t of the
optical
elements,
principally
the
two
Si(111)
m o n o c h r o m a t o r crystals, a n d a m o n o c h r o m a t i c b e a m
w a s s u c c e s s f u l l y t r a n s m i t t e d . All s u c h m a n i p u l a t i o n s
b e c a m e m u c h easier in July with t h e t r e m e n d o u s
i n c r e a s e in flux p r o d u c e d by t h e W 6 1 m i n i g a p
wiggler. T h i s d e v i c e w a s installed with t h e largest of
the t h r e e available v a c u u m c h a m b e r s . S o o n after,
first test m e a s u r e m e n t s w e r e m a d e with t h e t w o
d e t e c t o r s y s t e m s of t h e p o w d e r d i f f r a c t o m e t e r a n d
with t h e X T M s y s t e m .
T h e m a g n e t i c field s t r e n g t h , a n d h e n c e the hard X ray flux, i n c r e a s e s a p p r o x i m a t e l y e x p o n e n t i a l l y as t h e
w i g g l e r g a p is d e c r e a s e d . A l t h o u g h t h e installed v a c u u m c h a m b e r a l l o w e d a g a p of 18 m m , a n d t h e S L S
m a c h i n e c o u l d p r o d u c e in e x c e s s of 2 0 0 m A of stable
b e a m current, w e w e r e limited t o g a p s of 2 5 m m a n d
c u r r e n t s of 50 m A until w e c o u l d install o u r h i g h p o w e r c a r b o n filter in t h e f r o n t - e n d s y s t e m . T h i s
rotating d e v i c e , d e s i g n e d at PSI a n d d e s c r i b e d in t h e
contribution of G. H e i d e n r e i c h , et al., n o w lets us
w o r k at the m i n i m u m g a p a l l o w e d by t h e w i g g l e r
c h a m b e r . Installed in t h e f r o n t - e n d at t h e s a m e t i m e
w e r e t w o p h o t o n b e a m position m o n i t o r s , to p e r m i t
r e c o r d i n g t h e vertical b e a m position with m i c r o m e t e r
accuracy.
MILESTONES
A l o n g with t h e o t h e r p h a s e - l S L S b e a m l i n e s , t h e M a terials S c i e n c e B e a m l i n e s a w "first light" a n d underw e n t c o m m i s s i o n i n g in 2 0 0 1 . T h e f o l l o w i n g w e r e t h e
major milestones:
18.05.01
First light ( f r o m a b e n d i n g m a g n e t )
10.07.01
Monochromatic beam
26.07.01
W i g g l e r installed
17.08.01
P D : microstrip d e t e c t o r
22.08.01
PD: analyser detector
03.09.01
XTM
15.10.01
Rotating C-filter a n d b e a m m o n i t o r s
20.11.01
Horizontally f o c u s i n g crystal
T h e s h i e l d e d a n d control h u t c h e s h a d b e e n installed
earlier, a l o n g w i t h t h e f r o n t - e n d s a f e t y s y s t e m a n d
the m a j o r optical c o m p o n e n t s . W h e n the radiation
s y s t e m b e c a m e o p e r a b l e , it w a s p o s s i b l e t o p l a c e a
f l u o r e s c e n t s c r e e n b e h i n d a w i n d o w in t h e optics
hutch a n d t o o p e n t h e f r o n t - e n d shutter, p r o d u c i n g
WIGGLER SPECTRUM
C h a n g i n g the e n e r g y of t h e b e a m l i n e o p t i c s r e q u i r e s
the precise c h a n g e in setting of 11 s t e p p i n g m o t o r s .
T h i s p r o c e d u r e h a s b e e n integrated into a single,
user-friendly E P I C S c o m m a n d , with w h i c h it w a s p o s sible to e x p e r i m e n t a l l y d e t e r m i n e t h e w i g g l e r s p e c t r u m ( e x p r e s s e d in m o n o c h r o m a t i c p h o t o n s per s e c o n d exiting t h e o p t i c s h u t c h ) .
Fig. 2 s h o w s a c o m p a r i s o n of this m e a s u r e d flux with
the prediction for the g a p a n d m a c h i n e c u r r e n t u s e d
(violet c u r v e ) . Note that p h o t o n s w e r e o b s e r v e d o v e r
the entire s p e c i f i e d e n e r g y r a n g e . " A s set" refers to
an intensity m e a s u r e m e n t i m m e d i a t e l y after u s i n g t h e
automatic energy change program, and "optimized"
refers to s u b s e q u e n t fine t u n i n g . T h e r e m a i n i n g
difference b e t w e e n e x p e r i m e n t a n d prediction is
attributed t o a c u r v a t u r e of the first m o n o c h r o m a t o r
crystal, d u e t o i m p r o p e r m o u n t i n g . T h e r e m a i n i n g
theoretical c u r v e s in Fig. 2 s h o w future e x p e c t a t i o n s ,
w h e n t h e n a r r o w e r w i g g l e r c h a m b e r s are installed
a n d higher m a c h i n e c u r r e n t s b e c o m e s t a n d a r d .
53
BL-4S F l u x (Nov. 2001)
's™
l—1—1
:
/
c
o
o
y
j
—1
1—i
/ / ^—_
1 50 m A ~ - -
//
!
1
¡
1
!
•• •
^
""^-^
0,5 mm
! ih
r i
; i
r f
¡
1—1—
1
1
i u
50 m A
? mm
as set \
" \
!
!—!
-j
i
1
to m a n y potential b e a m l i n e u s e r s . T h e X T M g r o u p
w i s h e s to use p h a s e c o h e r e n c e to e n h a n c e the c o n trast of w e a k l y - s c a t t e r i n g biological a n d o t h e r l o w - Z
s a m p l e s , a n d s e v e r a l g r o u p s h a v e e x p r e s s e d interest
in e x p l o r i n g c o h e r e n t diffraction p h e n o m e n a .
T h e large effective horizontal s o u r c e size p r e s e n t e d
by t h e w i g g l e r basically d e s t r o y s all c o h e r e n c e in t h e
horizontal direction. T h a t t h e vertical c o h e r e n c e is not
d e s t r o y e d , in spite of the n u m e r o u s b e a m l i n e w i n d o w s , optical e l e m e n t s , a n d a b o v e all t h e rotating
c a r b o n filter, is d e m o n s t r a t e d by a h i g h - r e s o l u t i o n
r a d i o g r a m t a k e n with t h e X T M s y s t e m (Fig. 4 ) .
1
0
10
20
30
40
50
E (keV)
F i g . 2: Predicted and measured wiggler fluxes.
FOCUSING OPTICS
W i t h the v e r y helpful addition of a h o m e - m a d e "X-ray
eye", c o n s i s t i n g , in a single m o d u l e , of a scintillator, a
l e a d - g l a s s protection plate, a s h o r t - w o r k i n g - l e n g t h
lens, a n d a f r a m e - g r a b b i n g C C D c a m e r a , it w a s p o s sible to o p t i m i z e t h e f o c u s i n g optics (crystal 2 a n d
mirror 2). A n o p t i m a l l y f o c u s e d s p o t at 15 k e V p h o t o n
e n e r g y is s h o w n in Fig. 3.
Focused Spot, 15 keV
1 I 1 I
1 I 11
1 I 1 I
11
Y
M i l l
'
• ' '
* • ' '
F i g . 4: A high-resolution X T M
image
showing
interference lines indicative of vertical c o h e r e n c e
(courtesy of M. S t a m p a n o n i , E T H Z ) .
T h e i m a g e is of a 15 \im d i a m e t e r t u n g s t e n w i r e in a
100 [im d i a m e t e r b o r o n s h e a t h , a n d it w a s t a k e n at
1 7 k e V , with a s a m p l e - d e t e c t o r d i s t a n c e of 6 0 c m .
C l o s e i n s p e c t i o n s h o w s fine horizontal interference
stripes, s u g g e s t i n g a vertical c o h e r e n c e length of
s e v e r a l t e n s of urn.
1111
Ved ¡cal
"PILOT" USER OPERATION
Hori :ontal
• • • • '
-2
-1,5
-1
-0,5
0
0,5
1
1,5
2
Distance (mm)
In N o v e m b e r a n d D e c e m b e r , 2 0 0 1 , the b e a m l i n e
h o s t e d t h e X T M c o l l a b o r a t i o n , 9 p o w d e r diffraction
users, 2 reflectometry users and 1 spectroscopy
user.
ACKNOWLEDGEMENT
F i g . 3: V e r t i c a l a n d horizontal s c a n s t h r o u g h a foc u s e d s p o t at t h e P D s t a t i o n .
T h e resulting s p o t size, d e f i n e d by t h e full w i d t h s at
half m a x i m u m , is s m a l l e r t h a n 6 0 0 x 6 0 0 u r n .
2
COHERENCE
A l t h o u g h not an original d e s i g n g o a l , t h e p h a s e c o h e r e n c e of the h a r d X - r a y light is of great i m p o r t a n c e
T h e b e a m l i n e g r o u p w i s h e s t o sincerely t h a n k their
m a n y c o l l e a g u e s w i t h i n t h e S L S a n d at PSI at large
for their c h e e r f u l a n d e x p e r t a s s i s t a n c e .
REFERENCE
[1]
B.D.Patterson,
R. A b e l a ,
Chimia, 55, 5 3 4 ( 2 0 0 1 ) .
J.F. v a n der V e e n ,
54
COMMISSIONING OF THE PROTEIN CRYSTALLOGRAPHY BEAMLINE X06SA
C. Schulze-Briese,
T. Tomizaki,
C. Pradervand,
R. Schneider,
M. danousch,
W. Portmann,
G. Ingold, D. Rossetti, B. Frauenfelder,
C. Zumbach,
P. Hottinger,
Ch. Brönnimann,
E.F.
Q. Chen,
Eikenberry
The protein crystallography
beamline
(PX) X06SA was commissioned
in 2001 and will become
available
for regular
user operation
in March 2002. All major hardware
components
and the integrated
data
acquisition
and control
system
work well, and the major operational
goals - micro-focussing,
highresolution
diffraction
and MAD - could be achieved. The novel concept of producing
hard X-rays from the
higher harmonics
of an in-vacuuminsertion
device on a medium
energy synchrotron
could be
realised
without problems
and it was demonstrated
that top-up operation
has no detrimental
effect on the data
quality even without gating the data collection.
A number of structures
were solved, both de-novo and by
molecular
replacement.
The K-goniometer,
the MAR flat panel detector, a prototype
pixel detector and the
p-diffractometer
will become
available
in 2002. Substantial
improvements
are envisaged
for
beam
diagnostics
and data
management.
INTRODUCTION
Optical system
T h e S L S protein c r y s t a l l o g r a p h y b e a m l i n e w a s c o m missioned with a reduced hardware and software
c o n f i g u r a t i o n , n a m e l y t h e U 2 4 undulator, t h e final
optical s e t u p , t h e h i g h - r e s o l u t i o n d i f f r a c t o m e t e r w i t h a
single (|>-axis a n d M A R i m a g e plate a n d C C D d e t e c t o r s . T h e i n t e g r a t e d control a n d d a t a a c q u i s i t i o n
s y s t e m w a s c o m m i s s i o n e d s i m u l t a n e o u s l y w i t h first
user e x p e r i m e n t s . A total of 7 0 user shifts w a s delive r e d t o 14 g r o u p s , 6 of t h e m f r o m industry.
In a first test of t h e m i c r o - f o c u s s i n g capabilities of the
optical s y s t e m , t h e b e a m w a s f o c u s s e d to 2 5 by
3 8 u r n o n J u l y 1 1 . T h e v a l u e s later i m p r o v e d t o 2 0
by 3 0 u r n . After the installation of a n i m p r o v e d sagittal b e n d e r w i t h a significantly better crystal, t h e d e s i g n
v a l u e s of 10 by 2 5 | j m w e r e r e a c h e d . T h e b e a m s i z e
c a n be a d j u s t e d i n d e p e n d e n t l y in t h e horizontal a n d
vertical p l a n e , in o r d e r t o f o c u s o n the d e t e c t o r or to
match
the
sample
dimensions.
The
energy
reproducibility of t h e m o n o c h r o m a t o r is better t h a n
0.1 e V a n d v i b r a t i o n s are s m a l l e r t h a n 0.15 u r a d r m s .
T h e limited positional stability of t h e s y s t e m d u r i n g
e n e r g y s c a n s will b e i m p r o v e d by t h e installation of
C V D - d i a m o n d b a s e d X - r a y b e a m position m o n i t o r s in
2002.
COMMISSIONING
U24
First b e a m f r o m the U 2 4 u n d u l a t o r w a s a v a i l a b l e in
the o p t i c s h u t c h in late M a y 2 0 0 1 . T h e u n d u l a t o r
spectrum measured with a 10-mm gap showed good
a g r e e m e n t w i t h t h e o r y ( s e e Fig. 1 ). T h e a b s o l u t e flux
s e e m s to b e w i t h i n a f a c t o r of t w o w i t h t h e o r y . It
s h o w e d that t h e p h o t o n flux d e l i v e r e d by t h e u n d u l a t o r
crucially d e p e n d s o n t h e a l i g n m e n t of the e l e c t r o n
b e a m position a n d a n g l e w i t h the a p e r t u r e s in t h e
front e n d . M o r e o v e r , it c o u l d be d e m o n s t r a t e d that by
m i n i m i s i n g the orbit b u m p in the straight s e c t i o n 6 S
the lifetime r e m a i n s c o n s t a n t d o w n t o t h e m i n i m a l g a p
of 6.5 m m .
X06S ID Stan, M mm Gap
~\
2
t h
2
2
Detectors
D a t a a c q u i s i t i o n s t a r t e d w i t h a n i m a g e plate d e t e c t o r
kindly p r o v i d e d by t h e PSI Structural B i o l o g y G r o u p .
A l t h o u g h it is well suited for large unit cell s t r u c t u r e s ,
its r e a d - o u t t i m e e x c e e d s typical data a c q u i s i t i o n
t i m e s of 2-20 s e c o n d s per f r a m e by m o r e t h a n o n e
o r d e r of m a g n i t u d e . T h e m a r C C D d e t e c t o r w a s installed in early S e p t e m b e r a n d a data set of T h a u m a t i n w a s c o l l e c t e d within 1.5 h o u r at a b e a m c u r r e n t
of 2 0 m A , yielding a n e l e c t r o n d e n s i t y m a p of 1.3 Â
resolution.
T h e m a r C C D will b e u p g r a d e d t o t h e n e w m a r Flat
P a n e l D e t e c t o r o n c e this d e t e c t o r b e c o m e s a v a i l a b l e .
T h e d e c i s i o n t o p u r c h a s e this d e t e c t o r i n s t e a d of t h e
Large A r e a C C D D e t e c t o r [1], w a s t a k e n in c o n s e n s u s
w i t h user r e p r e s e n t a t i v e s . It is m a i n l y m o t i v a t e d by t h e
o u t s t a n d i n g p o i n t - s p r e a d f u n c t i o n , t h e large d y n a m i c
r a n g e , the large n u m b e r of r e s o l v a b l e diffraction orders, the e a s e of o p e r a t i o n a n d t h e v e r y g o o d test
results a l r e a d y o b t a i n e d w i t h a p r o t o t y p e of t h e F P D .
10
12
14
IS
IB
F i g . 1 : Measured and theoretical spectrum with a gap
of 10 m m . T h e t h e o r e t i c a l c u r v e i n c l u d e s a p h a s e
error of 2.5 ° a n d a n e l e c t r o n e n e r g y s p r e a d of 1.8 %o.
A first test of a single m o d u l e of t h e P I L A T U S pixel
d e t e c t o r d e m o n s t r a t e d its o u t s t a n d i n g point s p r e a d
f u n c t i o n a n d its potential for fine sliced data a c q u i s i tion. A further test u s i n g a b o a r d of 3 m o d u l e s a l l o w e d
t h e collection of a full d a t a set by t r a n s l a t i n g the d e vice in the vertical direction [2].
55
Diffractometers
T h e d e s i g n of t h e H i g h - R e s o l u t i o n d i f f r a c t o m e t e r follows t h e i n n o v a t i v e c o n c e p t of G . R o s e n b a u m [3]. It is
e q u i p p e d with a high s p e e d , high precision <|)-axis w i t h
fully m o t o r i s e d g o n i o m e t e r h e a d , a h i g h - r e s o l u t i o n
s a m p l e m o u n t i n g m i c r o s c o p e with c o n d e n s e r illumination a n d a fast Si-drift f l u o r e s c e n c e detector. T h e k g o n i o m e t e r is currently b e i n g installed at t h e H i g h R e s o l u t i o n diffractometer, w h i l e t h e u-diffractometer
will be d e l i v e r e d b y t h e e n d of t h e year.
facto s t a n d a r d b e a m l i n e control G U I at t h e E S R F , t o
facilitate t h e familiarisation of t h e u s e r s (Fig. 3).
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Operation a n d First Results
t ^ i i ^ u n . (\a fitttr«
B e a m stability w a s f o u n d t o be g o o d a n d not t o b e
affected by t h e c o n t i n u o u s injection in t o p - u p m o d e . A
p r e l i m i n a r y investigation s h o w e d o n l y a negligible
influence of t h e injection m o d e o n t h e data quality.
H e n c e , t o p - u p m o d e h a s b e c o m e t h e favourite
o p e r a t i o n m o d e for u s e r runs.
Several M A D a n d S A D experiments were carried out
at t h e Hg L e d g e a n d at t h e S e K-edge. T h e
a n o m a l o u s P a t t e r s o n m a p s w e r e of g o o d quality a n d
a l l o w e d t h e p h a s i n g of large s t r u c t u r e s e v e n with
small a n o m a l o u s signals. M o r e t h a n 15 s t r u c t u r e s
were solved by molecular replacement.
I rffPrm-HU l^nmnttir-i
1 Limn ttniiiliHi I- "ri
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It w a s possible t o resolve m o r e t h a n 3 1 0 diffraction
o r d e r s , b e i n g e q u i v a l e n t to a spot s e p a r a t i o n of 6.5
pixel by f o c u s s i n g t h e b e a m o n t h e m a r C C D detector.
II -.lr.l-t.l-. tutll»
I»
ùnr>tn*ft-ij p i f f ( H _ f
* u BG3 MB available
:
:
Hm«H ....iH
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F i g . 3: S n a p s h o t of a b e a m l i n e control G U I .
M o n i t o r i n g t h e d e v i c e p a r a m e t e r s in real t i m e a n d
b r o a d c a s t i n g t h e m to t h e clients w e r e not u s e d to
a v o i d u n e x p e c t e d n e t w o r k p r o b l e m s . T h i s f e a t u r e will
be installed before start of regular user o p e r a t i o n t o
realise a u t o l o g g i n g a n d c o m m a n d script g e n e r a t i o n .
SOFTWARE AND THE BACKUP
F i g . 2 : a) Part of a diffraction pattern b ) M a g n i f i e d
v i e w of reflections c o r r e s p o n d i n g t o a cell axis of m o r e
t h a n 4 0 0 Â at a d e t e c t o r d i s t a n c e of 2 0 0 m m .
The integrated data acquisition system
T h e b e a m l i n e control s e r v e r a n d t h e clients w o r k e d
well during t h e c o m m i s s i o n i n g . T h e m a r C C D , t h e
P I L A T U S detector, t h e h i g h resolution C C D c a m e r a ,
m a c h i n e p a r a m e t e r s , all t h e m o t o r s a n d t h e s e n s o r s
on t h e b e a m l i n e a r e c o n t r o l l e d or m o n i t o r e d b y t h e
s e r v e r s i m u l t a n e o u s l y t h r o u g h G U I o r C U I clients. T h e
d e a d t i m e (<5 s e c ) b e t w e e n e x p o s u r e s w a s highly
o p t i m i s e d f o r t h e m a r C C D . T h u s , it e n a b l e s u s e r s to
collect a data v o l u m e of m o r e t h a n 5 0 G B ( 6 0 0 0 i m a g e s ) p e r d a y . S i n c e c o m m i s s i o n i n g started, n o softw a r e failures w e r e o b s e r v e d d u r i n g user's data collection s e q u e n c e s . T h i s p r o v e s that t h e client s e r v e r
s y s t e m is fairly reliable for practical user e x p e r i m e n t s .
C o m m a n d script g e n e r a t o r a n d history d a t a b a s e a r e
a l s o t e s t e d u s i n g a local d a t a b a s e s e r v e r r u n n i n g o n
an S G I w o r k s t a t i o n .
S i n c e g r o u p a c o u n t s a n d t h e virtual u s e r office w e r e
not i m p l e m e n t e d during t h e c o m m i s s i o n i n g , t h e s e r v e r
worked without database connection. T h e appearance
of t h e G U I client w a s build similar to P r o D C [4], a de
The C C P 4 package, M O S F L M , and X D S were installed o n t h e central s e r v e r f o r data p r o c e s s i n g . A
Linux cluster with 2 C P U s a n d s e v e r a l G i g a b y t e s of
m e m o r y will be p u r c h a s e d v e r y s o o n . Initial p h a s i n g
software, s u c h a s S O L V E , S n B a n d S H E L X will be
a l s o installed to a c h i e v e t h e m a x i m u m efficiency of
S A D a n d M A D e x p e r i m e n t s . U s e r s will h a v e different
accounts on the beamline and PSI network. However,
t h e s a m e c o m p u t i n g e n v i r o n m e n t with s o p h i s t i c a t e d
security will be d e d i c a t e d to t h e u s e r s .
D L T t a p e s a n d F T P a c o u n t s with p a s s w o r d s a r e
available t o t h e u s e r s . Industrial u s e r s w e r e p l e a s e d
with t h e security of t h e s y s t e m . F T P w a s v e r y useful
t o t r a n s f e r small d a t a s e t s to r e s p o n d to u r g e n t r e q u e s t s f r o m u s e r s . T h e P S I L T O t a p e library with a
s t o r a g e c a p a c i t y of 2 5 T B will b e c o m e available m i d
2 0 0 2 t o store users' d a t a s e t s for l o n g e r p e r i o d s .
REFERENCES
[1]
C. S c h u l z e - B r i e s e et a l . ,
2000, Volume VII.
PSI
Scientific
[2]
C. B r ö n n i m a n n et a l . , PSI Scientific R e p o r t 2 0 0 0 ,
Volume VII.
[3]
http://www.esrf.fr/computing/bliss/gui/prodc
[4]
http://www.sbc.anl.gov
Report
56
LAYOUT OF THE MICROXAS BEAMLINE: DESIGN STUDY
D. Grolimund,
A.M. Scheidegger,
J.F. van der Veen,
R.
Abela
Over the past few years, the advancement
of X-ray Absorption
Spectroscopy
(XAS) towards
an
indispensable
analytical
tool resulted in a substantial
demand for synchrotron-based
beam line
facilities
optimized
for XAS experiments.
In view of the importance
of micro-scale
processes
in different
scientific
disciplines,
there has been a considerable
effort to develop high-resolution
analytical X-ray probes in the
hard X-ray regime using state-of-the-art
X-ray focusing devices. The design of the micro XAS beamline is
conceptualized
to yield monochromatic
X-ray beams with high energy resolution
combined
with
dynamic
microfocusing
capabilities.
A description
of the facility concept and the optical layout is provided
INTRODUCTION
T h e m i c r o X A S b e a m l i n e project is a joint effort of t h e
S w i s s X A S U s e r C o m m u n i t y for a n X - r a y a b s o r p t i o n
s p e c t r o s c o p y b e a m l i n e at the S w i s s Light S o u r c e
(SLS)
T h e project is s u p p o r t e d by 2 6 r e s e a r c h
g r o u p s at P S I , o t h e r N a t i o n a l R e s e a r c h L a b o r a t o r i e s
(EAWAG,
EMPA, W S L , and
IUL), a n d
Swiss
Universities ( E T H Z , E P F L , Universities of G e n e v a ,
L a u s a n n e , B a s e l , a n d B e r n ) , w h i c h all c o n t r i b u t e d a
scientific c a s e t o the m i c r o X A S p r o p o s a l .
T h e m i c r o X A S b e a m l i n e at the S L S is d e s i g n e d as a n
analytical facility d e d i c a t e d t o s y n c h r o t r o n b a s e d m i c r o - b e a m X - r a y a b s o r p t i o n s p e c t r o s c o p y . T h e optical
c o n c e p t is o p t i m i z e d r e g a r d i n g m i c r o f o c u s i n g with a
spatial resolution in t h e o r d e r of 1x1 u r n u s i n g a high
resolution m o n o c h r o m a t i c X - r a y b e a m of e n e r g i e s
ranging f r o m 4 k e V t o ~ 1 8 k e V (with a n e n e r g y r e s o l u tion A E / E < 1 0 " ) . T h e b e a m c h a r a c t e r i s t i c s fulfill all t h e
n e c e s s i t i e s r e q u i r e d for o p t i m i z e d X A S m e a s u r e m e n t s
s u c h a s spatial stability, high p h o t o n flux a n d flux d e n sity, high e n e r g y r e s o l u t i o n , a n d m i n i m i z e d c o n t a m i nation by high e n e r g y radiation ( h a r m o n i c s ) . B e s i d e s
h i g h - r e s o l u t i o n X A S a n d related t e c h n i q u e s , a d d i t i o n a l
e x p e r i m e n t a l capabilities include X - r a y F l u o r e s c e n c e
( X R F ) a n d 2 D / 3 D i m a g i n g t e c h n i q u e s . Finally, it is
f o r e s e e n that t h e m i c r o X A S b e a m l i n e will be l o c a t e d
in a long straight s e c t i o n e q u i p p e d with a radiator a n d
in addition a m o d u l a t o r (Fig. 1). T h i s c o n f i g u r a t i o n
a l l o w s for p r o d u c i n g f e m t o - s e c o n d X - r a y p u l s e s t o
s t u d y t i m e - d e p e n d e n t p h e n o m e n a in c o n d e n s e d
m a t t e r relevant t o p h y s i c s , c h e m i s t r y , biology, or e n v i ronmental science.
2
4
PROPOSED BEAMLINE LAYOUT
S e v e r a l optical s c h e m e s w e r e e v a l u a t e d in r e s p e c t to
spatial r e s o l u t i o n , p h o t o n flux, e n e r g y r e s o l u t i o n ,
c o s t s , c o m p l e x i t y a n d m e c h a n i c a l stability, a n d a f a v o r e d optical layout of t h e m i c r o X A S b e a m l i n e h a s
b e e n identified.
T h e s c h e m a t i c s of t h e p r o p o s e d layout of t h e S L S m i c r o X A S b e a m l i n e is d e p i c t e d in Fig. 2. A mini-gap, invacuum
undulator
(U17) s e r v e s a s radiation s o u r c e
[2]. T h e front-end i n c l u d e s S L S s t a n d a r d radiation
F i g . 1 : Floor plan of t h e S L S s h o w i n g the existing
b e a m l i n e s a n d p r o p o s e d location of t h e m i c r o X A S
beamline.
s a f e t y e q u i p m e n t as well as a n a p e r t u r e s y s t e m to
r e d u c e b r e m s s t r a h l u n g a n d total radiation p o w e r [ ].
T h e s e a p e r t u r e s in t h e f r o n t - e n d d e f i n e t h e m a x i m a l
angular
extension
of
the
photon
beam
to
2 5 0 x 100 u r a d . T h e first optical e l e m e n t , a toroidal
mirror, is located at a d i s t a n c e of ~ 1 6 m f r o m the m i d point of t h e undulator. T h i s w a t e r - c o o l e d d e v i c e is
o p e r a t e d in g r a z i n g - i n c i d e n c e m o d e , d y n a m i c a l l y
bent, a n d p r o d u c e s a horizontal 1.3:1 f o c u s i n g a n d a
c o l l i m a t i o n of t h e b e a m in t h e vertical d i r e c t i o n . B e t w e e n this mirror a n d its horizontal f o c u s point at
- 3 1 m , the monochromator
is p l a c e d at - 2 0 m . T h i s
fixed-exit c r y o g e n i c - c o o l e d d e v i c e is e q u i p p e d with
t w o s e t s of m o n o c h r o m a t o r crystals, n a m e l y S i ( 1 1 1 )
a n d S i ( 2 2 0 ) . A t the horizontal f o c u s point t h e b e a m is
p a s s i n g a d y n a m i c 'roller-blade'
slit system
before
e n t e r i n g t h e Kirkpatrick-Baez
(KB) mirror
system.
Using such a two-step strategy to focus the X-ray
b e a m , the d e s i g n g o a l of a final s p o t s i z e of 1x1 u r n
c a n be a c h i e v e d a n d e v e n s u r p a s s e d . H o w e v e r , t h e
m a x i m i z e d p h o t o n flux d e n s i t y is a l r e a d y r e a c h e d at a
b e a m size of - 6 x 1 u m . A n y further r e d u c t i o n of s p o t
size results in a c o r r e s p o n d i n g r e d u c t i o n in total p h o t o n flux. T h e b e a m l i n e c o n c e p t is b a s e d o n a n o p e n
d e s i g n p h i l o s o p h y a n d will b e c o m p a t i b l e with t h e
possibility of f u t u r e d e v e l o p m e n t s . For e x a m p l e , m u l tiplayer optics a n d diffractive f o c u s i n g optics are inv e s t i g a t e d a s potential f u t u r e optical d e v i c e s .
3
2
2
2
57
side view
crystal
point
distance between elements [mm]
13971
I
0
2009
4000
1
1
13971
15980
110O0
1
4000
1
19980
30980
distance to source point [mm]
200
1
34980
200
1
35180
1
35380
F i g . 2: S c h e m a t i c r e p r e s e n t a t i o n of t h e p r o p o s e d optical layout of t h e m i c r o X A S b e a m l i n e at S L S . N o t e that t h e
toroidal mirror f o c u s e s t h e b e a m in t h e horizontal direction (1.3:1 d e m a g n i f i c a t i o n ) but c o l l i m a t e s t h e X - r a y s in t h e
vertical direction.
T h e e x p e r i m e n t a l station will b e e q u i p p e d with
2 optical b e n c h e s . T h e first b e n c h will host m e a s u r e m e n t s , w h i c h d o not n e c e s s a r i l y require a m i c r o - b e a m
(e.g., in-situ
studies and non-standard techniques
s u c h a s laser i n d u c e d f e m t o - s e c o n d a p p l i c a t i o n s ) .
T h e s e c o n d optical b e n c h is hosting t h e K B mirror pair
a n d is d e d i c a t e d to m i c r o b e a m a p p l i c a t i o n s . T h e
b e a m l i n e will b e e q u i p p e d with m o t o r i z e d s a m p l e
s t a g e s (xyz, <p, 0), w h i c h s h o u l d a l l o w - in addition t o
m i c r o X A S a n d X R F - m a p p i n g - for t e c h n i q u e s s u c h as
G r a c i n g - l n c i d e n c e X - r a y A b s o r p t i o n Fine S t r u c t u r e
(GI-XAFS) and X-ray Standing W a v e s (XSW). A mot o r i z e d optical m i c r o s c o p e a n d a C C D c a m e r a will b e
available for b e a m m o n i t o r i n g a n d s a m p l e a l i g n m e n t .
Detector s y s t e m s a v a i l a b l e in a first p h a s e are a multie l e m e n t G e (or SiLi) solid-state d e t e c t o r a n d a S t e r n H e a l d d e t e c t o r s y s t e m . E l e m e n t a l distributions c a n be
m a p p e d with a spatial r e s o l u t i o n of 1x1 u r n using a
high s p e e d x - y - z s c a n n i n g s t a g e with e n e r g y dispersive f l u o r e s c e n c e d e t e c t i o n .
2
REFERENCES
[]
A . M . S c h e i d e g g e r , R. Prins, Joint proposal
Swiss XAS user community
for an EXAFS
line for heterogeneous
and dilute systems
Swiss Light Source (SLS), 2 0 0 0 .
[]
G. Ingold et al., Hard X-ray insertion devices
for
high brightness/high
flux: U24, U17, W60, PSI
Scientific R e p o r t 1 9 9 9 , V o l u m e V I I .
[]
Q. C h e n et al., S L S frontends
for insertion
device
beamlines,
PSI Scientific R e p o r t 1 9 9 9 , V o lume VII.
1
2
3
by the
beamat the
58
INSERTION DEVICES: FIRST EXPERIENCES
G. Ingold, T.
Schmidt
In 2001, we concentrated
on the construction,
the magnetic measurement
and the installation
of 5 Insertion
Devices (IDs) (including the ID vacuum chamber) serving 4 beamlines.
The commissioning
of all IDs and
the conditioning
of the chambers
went smoothly.
Whatever the gap value, the effect of all the IDs on the
closed orbit is small and within specification
in terms of magnetic field errors acting on the trajectory of the
electron beam. An important
goal has been reached with the UE212 electromagnetic
elliptical
undulators.
Operated
in the quasi-periodic
field mode, the spectral flux on harmonic
3 is suppressed
by more than
two orders of magnitude
as compared
to a convential
undulator.
Such a suppression
is needed to allow
photoemission
experiments
at the Fermi edge planned at the SIS-beamline.
The commissioning
of the
elliptical polarized
operation
mode of both the UE212 twin-undulator
(SIS-beamline)
and the UE56 twinundulator (SIM-beamline)
is in progress. At the PX beamline, the U24 in-vacuum
undulator is now
routinely
operated at higher harmonics,
demonstrating
that the concept of using small-gap,
short-period
undulators
to extend the high brightness
radiation at medium energy light sources is valid. The short-period
wiggler
W61 installed at the MS-beamline
operates at a minimum gap of 11.5 mm using a vacuum chamber
with
8 mm beam stay-clear
aperture.
INTRODUCTION
T h e I D - b a s e d p h o t o n s o u r c e s [1] at t h e S L S c o v e r t h e
e n e r g y r a n g e 10 e V to 4 0 keV. T h e e n e r g y r a n g e 10 e V
to 18 k e V is c o v e r e d by u n d u l a t o r s , a n d for p h o t o n e n e r g i e s u p to 4 0 keV, a hybrid wiggler is e m p l o y e d . To
a c h i e v e high flux a n d b r i g h t n e s s at a s t o r a g e ring of
2.4 GeV, s m a l l - g a p u n d u l a t o r s a n d w i g g l e r s h a v e to b e
installed. T h e notable f e a t u r e s of t h e I D - b a s e d p h o t o n
s o u r c e s at t h e S L S are:
• For soft X - r a y s : (i) T h e u s e of elliptical t w i n - u n d u l a t o r s
with variable linear a n d circular polarisation in t h e e n e r g y r a n g e 8 e V - 2 keV, allowing oppositely p o l a r i z e d ,
rapidly s w i t c h e d (0.01-1 k H z ) b e a m s u n d e r o t h e r w i s e
identical conditions, (ii) A q u a s i - p e r i o d i c field c o n f i g u r a tion is u s e d to s u p p r e s s t h e spectral flux on higher harm o n i c s to allow p h o t o e m i s s i o n s p e c t r o s c o p y at 10 eV.
• For h a r d X - r a y s : (i) T h e u s e of s m a l l - g a p , s h o r t p e r i o d u n d u l a t o r s to e x t e n d t h e high b r i g h t n e s s
s y n c h r o t r o n radiation to ~ 18 keV, o p e r a t i n g o n higher
h a r m o n i c s (9th-13th). (ii) T h e u s e of a small p e r i o d
wiggler o p t i m i z e d for high horizontal flux in t h e e n e r g y
r a n g e 5-40 keV.
F i g . 1 : D o w n left, right side: T h e U E 2 1 2 elliptical t w i n u n d u l a t o r (10 m ) , installed in t h e S L S s t o r a g e ring. T h e
m a g n e t c h i c a n e for fast polarization s w i t c h i n g will b e
installed b e t w e e n t h e undulator s e c t i o n s . A b o v e : Elect r o m a g n e t i c iron y o k e of o n e s e c t i o n (4.55 m) o p e r a t e d
D C to p r o v i d e ( quasi-periodic) vertical a n d horizontal
m a g n e t i c fields.
In t h e y e a r 2 0 0 1 , t h e following IDs h a v e b e e n installed:
• U 2 4 u n d u l a t o r ( i n - v a c u u m ) , April 10, 2 0 0 1 ; s h o r t
straight s e c t i o n 6 S ; S P r i n g - 8 (JP)/PSI c o l l a b o r a t i o n ;
P X - b e a m l i n e [2].
• U E 2 1 2 / 1 ( e l e c t r o m a g n e t i c , D C ) elliptical undulator,
July 3 0 , 2 0 0 1 ( U E 2 1 2 / 2 N o v e m b e r 12, 2 0 0 1 ) ; long
straight s e c t i o n 9 L ; d e s i g n : E L E T T R A ( l ) / P S I , c o n s t r u c t i o n : B I N P N o v o s i b i r s k (RU); S I S - b e a m l i n e [3].
• W 6 1 Wiggler, July 3 0 , 2 0 0 1 ; s h o r t straight s e c t i o n
4 S ; d e s i g n : P S I , c o n s t r u c t i o n : Danfysik ( D K ) ; M S b e a m l i n e [4].
• U E 5 6 / 1 ( S a s a k i / A P P L E II type) elliptical undulator,
N o v e m b e r 12, 2 0 0 1 ; m e d i u m straight s e c t i o n 1 1 M ;
P S I / B E S S Y (D) c o l l a b o r a t i o n ; S I M - b e a m l i n e [5].
In
this
paper
we
report
on
relevant
issues
con-
59
SOFT X-RAYS
T. Schmidt,
G. Ingold, W. Bulgheroni,
G.
Heidenreich, A. Imhof, B. Jakob, A. Keller, T.
Korhonen,
L. Patthey, L Pochmann,
M. Rohrer, C.
Quitmann,
L. Schulz, C. Vollenweider, P. Wiegand and R. Abela
(PSI); J. Bahrdt, H. Bäcker, W. Frentrup, A. Gaupp
(BESSY, D); P. Vobly, E. Antokhine, A. Utkin (BINP, Ru)
THE ELLIPTICAL UNDULATOR UE212
T h e e l e c t r o m a g n e t i c undulator U E 2 1 2 c o n s i s t s of t w o
identical s e g m e n t s U E 2 1 2 / 1 a n d U E 2 1 2 / 2 (Fig. 1) o p e r a t e d D C to p r o d u c e variable linear a n d elliptical polarized light in t h e e n e r g y range 8-800 eV. In addition, the
I
-20
i
i
i
-10
F i g . 2: Top: Vertical a n d horizontal first field integrals
in t h e region ± 2 0 m m horizontally, m e a s u r e d for the
U E 2 1 2 / 2 undulator for t h e vertical field in t h e range of
0.05-0.5 T ( 3 0 - 1 4 5 A ) . B o t t o m : Vertical field integrals
for horizontal fields of ± 0 . 0 5 T a n d ± 0 . 1 T m e a s u r e d
with z e r o a n d m a x i m u m vertical field. (An arbitrary
dipole offset is u s e d to displace the g r a p h s for clarity.)
6-
c e r n i n g the c o n s t r u c t i o n , the m a g n e t i c m e a s u r e m e n t s
a n d t h e first c o m m i s s i o n i n g results. T h e description of
t h e ID drive a n d control s y s t e m d e v e l o p e d at the S L S
is given in t w o s e p a r a t e p a p e r s [6, 7].
For all IDs, w e s p e c i f i e d t h e 1
( 2 ) field integrals to stay within h < ± 1 0 G c m ( l < ± 1 0 G c m )
in a ' g o o d field region' of x = ± 2 0 m m horizontally for
both t h e vertical a n d horizontal field c o m p o n e n t . O n
axis, before (after) c o m p e n s a t i o n the first a n d s e c o n d
field integral h a s to stay b e l o w 100 G - c m (30 G c m )
a n d 5 • 1 0 G c m (2 • 1 0 G c m ) repectively for both
field c o m p o n e n t s .
s t
2
4
2
3
nd
2
4
2
2
W h a t e v e r t h e g a p v a l u e , the m e a s u r e d effect of the
IDs on t h e c l o s e d orbit before c o m p e n s a t i o n is < 3 0
urn ( < 50¿¿m) for t h e u n d u l a t o r s (small g a p w i g g l e r ) ,
c o n s i s t e n t with the m a g n e t i c field error specification.
U s i n g c o r r e c t o r coils at both the up- a n d d o w n s t r e a m
e n d of the ID, the o b s e r v a b l e b e a m d i s p l a c e m e n t is
c o r r e c t e d to < I0¿¿m (after c o m p e n s a t i o n ) to allow the
e x p e r i m e n t e r to v a r y t h e g a p at will, o n c e t h e b e a m
distortion is m i n i m i z e d to ~ l ^ m by t h e slow orbit
f e e d b a c k [8].
T h e m e a s u r e d lifetime (12 h o u r s at 2 0 0 m A ) is determ i n e d by the b e a m stay-clear a p e r t u r e of the c h a m b e r
installed in the long straight section 9 L a n d d o e s not
c h a n g e w h e n t h e g a p of the U 2 4 i n - v a c u u m undulator
is c l o s e d to 6.5 m m . At t h e PX b e a m l i n e this u n d u lator is n o w routinely o p e r a t e d at higher h a r m o n i c s
(7th-11th) to r e a c h 8 - 1 2 . 7 keV.
F i g . 3: P h o t o e m i s s i o n s p e c t r u m m e a s u r e d at t h e S I S
b e a m l i n e using a quasi-periodic vertical field m o d u l a tion in the undulator U E 2 1 2 / 1 in c o m p a r i s o n to t h e periodic field m o d e . T h e s u p p r e s s i o n on h a r m o n i c 2 a n d
3 for e n e r g i e s c l o s e to the F e r m i e d g e is o p t i m i z e d by
c h a n g i n g t h e c u r r e n t ratio of t w o different circuits for the
vertical poles.
u n d u l a t o r s c a n be o p e r a t e d in a quasi-periodic m o d e
using field a m p l i t u d e m o d u l a t i o n , w h e r e a s u b s e t of
vertical poles is p o w e r e d by a different current using
t w o m a i n p o w e r supplies. After c o n s t r u c t i o n at BINP,
Novosibirsk, t h e u n d u l a t o r s have b e e n m e a s u r e d at
PSI both m e c h a n i c a l l y (using a H P laser interferometer) a n d m a g n e t i c a l l y (using a Hall-probe array a n d a
flip-coil s y s t e m built by B I N P a n d a s t r e t c h e d w i r e s y s t e m a s well a s a p u l s e d w i r e s y s t e m built by PSI). For
both fields, t h e first t w o poles at the e x t r e m e t i e s are
t u n e d to t a k e saturation effects d u r i n g a field r a m p into
a c c o u n t . L o n g coils are u s e d to c o r r e c t for a dipole a n d
a s k e w q u a d r u p o l e c o m p o n e n t . Both t h e m e c h a n i c a l
a n d the m a g n e t i c t o l e r a n c e s w e r e within s p e c i f i c a t i o n s
(Fig. 2 ) . For linear polarization, after c o m p e n s a t i o n , a
60
c l o s e d orbit distortion of ~ 10¿*m (rms) h a s b e e n m e a s u r e d vertically a n d horizontally.
For p h o t o e m i s s i o n spectroscopy, a n i m p o r t a n t feature
t e s t e d so far is the q u a s i - p e r i o d i c m o d e [9] to s u p p r e s s
t h e higher h a r m o n i c c o n t e n t at the f u n d a m e n t a l e n e r g y
after t h e m o n o c h r o m a t o r . T h e q u a s i - p e r i o d i c field m o d ulation, for t h e first t i m e u s e d in a n e l e c t r o m a g n e t i c u n dulator, c a n b e o p t i m i z e d for s u p p r e s s i o n of t h e 2 n d ,
3rd or e v e n higher h a r m o n i c s by adjusting the excitation
c u r r e n t s . C o m p a r e d to t h e periodic m o d e , a s u p p r e s s i o n of 1/125 h a s b e e n m e a s u r e d for the 3rd h a r m o n i c
(Fig. 3).
THE ELLIPTICAL UNDULATOR UE56
A first S a s a k i / A P P L E II u n d u l a t o r U E 5 6 / 1 with a period of 5 6 m m h a s b e e n installed for t h e S I M b e a m l i n e
(Fig.4). In c o l l a b o r a t i o n with BESSY, the s e c o n d u n d u lator U E 5 6 / 2 is currently u n d e r c o n s t r u c t i o n .
F i g . 5: U n d u l a t o r U E 5 6 / 1 installed with g a p c l o s e d in
t h e s t o r a g e ring. F r o m left to right: C o r r e c t o r coil, t a p e r
s e c t i o n (inside the e n d box of t h e ID v a c u u m c h a m b e r ) ,
limit s w i t c h e s , multipole c o r r e c t o r ('magic finger') a n d
p e r m a n e n t m a g n e t arrays ( N d F e B ) .
0 ° a n d 9 0 ° . T h e large m a g n e t i c f o r c e s t e n d to p u s h
t h e g a p m e c h a n i c a l l y o p e n w h e n t h e m a g n e t arrays are
shifted. A C s e r v o m o t o r s o p e r a t e d in c l o s e d loop (feedback) are u s e d to k e e p t h e g a p v a l u e at its setpoint
r e g a r d l e s s of t h e highly nonlinear m a g n e t i c forces d u e
to the shift m o t i o n [6, 7 ] .
F i g . 4:
U n d u l a t o r U E 5 6 / I installed in straight s e c t i o n
11M
T h e d e v i c e s are p u r e - p e r m a n e n t m a g n e t ( p p m )
s t r u c t u r e s . T h e m a g n e t a s s e m b l y is split into four m a g net arrays. Two m a g n e t arrays, o n e of the u p p e r a n d
o n e of the lower m a g n e t arrays are s i m u l t a n e o u s l y disp l a c e d longitudinally. T h e a s s o c i a t e d m o t i o n is c a l l e d
'the p h a s i n g ' or 'shift m o t i o n ' . A parallel shift results in
a c h a n g e of the circular polarization f r o m left to right
h a n d side. T h e anti-parallel shift p r o v i d e s linearly polarized light with a variable declination a n g l e b e t w e e n
Magnetically, t h e S a s a k i / A P P L E ll-type u n d u l a t o r s
are v e r y d e m a n d i n g d e v i c e s . For a c o m b i n e d g a p a n d
shift m o t i o n , o n e e x p e c t s to o b s e r v e t h r e e c l a s s e s of
p e r t u r b a t i o n s to t h e b e a m : c l o s e d orbit distortion, t u n e
shifts ( a n d a s s o c i a t e d b e t a t r o n beat) a n d a possible red u c t i o n of the d y n a m i c a p e r t u r e resulting in a s h o r t e r
lifetime. A p r o p e r s h i m m i n g a n d a l i g n m e n t as well as
a suitable d e s i g n of t h e e x t r e m e t i e s to p r o d u c e a disp l a c e m e n t free trajectory e n s u r e a small c l o s e d orbit
distortion. To control t h e field integrals within t h e s p e c ified limits, 2 - m a g n e t m o d u l e s have b e e n m o v e d vertically a n d horizontally (Virtual s h i m m i n g ' ) by 0.1 m m
d u r i n g the m a g n e t i c m e a s u r e m e n t . In a s e c o n d step,
multiple trim m a g n e t s are used('multipole corrector' or
' m a g i c finger'), installed at t h e e x t r e m e t i e s are u s e d .
H a v i n g o p t i m i z e d the field integral distribution for shift
- 2 8 m m (elliptical polarization) as s h o w n in Fig.5, the
field integrals c h a n g e for shift 0 m m (linear polarization). T h i s c h a n g e , still within t h e s p e c i f i e d limits, is d u e
to t h e non-unit p e r m e a b i l i t y of N d F e B ('¿t-1 effect'). To
c o r r e c t for this c h a n g e , m a g n e t s w a p p i n g rather t h a n
virtual s h i m m i n g s h o u l d be a p p l i e d for field o p t i m i z a tion. D e p e n d i n g o n t h e shift, a p h a s e error of 2 . 2 ° - 2 . 6 °
has been measured.
A l t h o u g h the U E 5 6 / 1 u n d u l a t o r h a s not b e e n corrected for the ¿t-1 effect, its influence on t h e b e a m is
s m a l l : Before c o m p e n s a t i o n , a c l o s e d orbit distortion of
A x ~ 10 ¿*m (rms) ( A y ~ 30 ¿*m (rms)) is o b s e r v e d horizontally (vertically) for the g a p (shift) range 18-150 m m
(-28 m m to + 2 8 m m ) . U s i n g c o r r e c t o r coils (feedforward
c o r r e c t i o n ) , the distortion is r e d u c e d to < 5 ¿*m ( r m s ) for
both p l a n e s . T h e vertical t u n e shift m e a s u r e d is AQ =
0 . 0 0 2 . C h a n g i n g t h e shift f r o m - 2 8 m m to 2 8 m m , the
y
61
t w e e n S P r i n g - 8 a n d PSI a n d is n o w routinely opera t e d at t h e PX b e a m l i n e in t h e e n e r g y range 8 14 k e V (Fig. 7). O u r e x p e r i e n c e c o n f i r m s that t h e c o n c e p t of e x t e n d i n g high b r i g h t n e s s u n d u l a t o r radiation at
m e d i u m e n e r g y light s o u r c e s to 5-18 keV o p e r a t i n g o n
higher h a r m o n i c s is valid.
100
n
-40
1
1
1
-20
0
x [mm]
20
r
40
Fig. 6: Top: Vertical a n d horizontal first field integrals
in t h e region ± 4 0 m m horizontally, m e a s u r e d for the
U E 5 6 / 1 u n d u l a t o r at m i n i m u m g a p (15 m m ) in t h e horizontal linear p o l a r i z e d field m o d e (shift -28 m m ) . Bott o m : C h a n g e of t h e first field integrals w h e n t h e shift
is c h a n g e d f o r m -28 m m to 0 m m (vertical field). T h i s
c h a n g e , still within t h e s p e c i f i e d limits for the field integrals, is d u e the non-unity p e r m e a b i l i t y of N d F e B
effect').
m e a s u r e d horizontal t u n e c h a n g e is A Q ^ - 0 . 0 0 1 5 .
THE MAGNET CHICANE
Both t h e U E 5 6 a n d the U E 2 1 2 elliptical t w i n - u n d u l a t o r s
will be o p e r a t e d in the ' c h i c a n e m o d e ' or in t h e ' p h a s e
m a t c h e d m o d e ' u s i n g a 7 - m a g n e t c h i c a n e . In the chic a n e m o d e , t h e e l e c t r o n trajectory is parallel d i s p l a c e d
by 1.6 m m (i.e. 10a of the horizontal b e a m size) t o allow a rapid s w i t c h i n g of the polarization in the b e a m line. To o p e r a t e the t w i n - u n d u l a t o r s as a single device,
b o t h s e g m e n t s have to be p h a s e m a t c h e d t o g u a r a n t e e c o n s t r u c t i v e interference of the light f r o m the t w o
u n d u l a t o r s . A n a n g u l a r kick of 3.3 m r a d is p r o d u c e d by
a 0.2 T field in the dipole c h i c a n e m a g n e t s . For both
b e a m l i n e s , t h e c h i c a n e will b e installed in t h e s u m m e r
of 2 0 0 2 .
HARD X-RAYS
G. Ingold,
T. Schmidt,
W.
T. Korhonen,
B. Patterson,
L.
L. Schulz, C. Schulze-Briese,
lenika and R. Abela
(PSI);
T. Tanaka (SPring-8, Jp)
Bulgheroni,
A. Keller,
Pochmann,
M. Rohrer,
C. Vollenweider,
S. ZeT. Hará, H.
Kitamura,
THE UNDULATOR U24 (IN-VACUUM)
T h e i n - v a c u u m undulator U 2 4 is a joint project be-
Fig. 7: U n d u l a t o r U 2 4 ( i n - v a c u u m ) installed at the
S L S s t o r a g e ring. T h e d e v i c e is m o u n t e d o n motorized m o v e r s for in-situ a l i g n m e n t . Szintillator p a d d l e s
m o u n t e d at the d o w n s t r e a m e n d are u s e d to m o n i t o r
t h e e l e c t r o n b e a m loss rate.
T h e u n d u l a t o r h a s t w o r e m o t e l y - c o n t r o l l e d motorizations. T h e m a i n o n e is d e d i c a t e d to m a g n e t i c - g a p
t u n i n g f r o m 6.5 to 3 8 m m at a m a x i m u m s p e e d of 1
m m / s a n d a resolution of 1 urn. T h e o t h e r o n e vertically translates a n d levels the full m a g n e t a s s e m b l y for
a p r e c i s e c e n t e r i n g a n d a l i g n m e n t with r e s p e c t t o the
e l e c t r o n b e a m . It is e x p e c t e d that in e x t r e m e situations
t h e g a p will be t h e limiting a p e r t u r e . T h i s m a y result in
a possible s c r a p i n g of t h e e l e c t r o n b e a m by t h e m a g net assembly. To c o n s t a n t l y m o n i t o r the loss rate, w e
have installed t w o scintillator p a d d l e s d o w n s t r e a m of
t h e undulator. T h e ID interlock m o n i t o r s t h e e l e c t r o n
b e a m position at the up- a n d d o w n s t r e a m t a p e r transitions a n d auto- matically o p e n s the g a p or d u m p s the
b e a m o n c e the e l e c t r o n b e a m trajectory e x c e e d s critical limits both in a n g l e a n d d i s p l a c e m e n t . I m p e d a n c e
effects m a y c a u s e an e x c e s s i v e h e a t i n g at t h e j u n c t i o n
b e t w e e n t h e flexible transitions a n d t h e m a g n e t a s s e m bly. N e w flexible, w a t e r c o o l e d t a p e r transitions have
b e e n d e v e l o p e d a n d t e s t e d for t h e g a p range 6-40 m m
62
p e r i o d of 17 m m a r e o p t i m i z e d to r e a c h a brilliance of
1.8 • 1 0 p h o t o n s / s / m m / m r a d at a r o u n d 14 keV. T h e
first U 1 7 undulator will r e p l a c e t h e U 2 4 d e v i c e p r e s e n t l y
installed at t h e P X - b e a m l i n e , t h e s e c o n d o n e will b e installed in s e c t i o n 5 L for t h e n e w ¿¿XAS-beamline.
T h e c o n c e p t u a l d e s i g n is f i n i s h e d a n d t h e specification
for a W T O call for t e n d e r is in p r e p a r a t i o n . A 2 - a x e s ID
drive a n d control s y s t e m d e v e l o p e d for s e r v o - m o t o r s
o p e r a t e d in c l o s e d loop [6, 7] will b e u s e d to control t h e
g a p parallelism to < 5 ¡im in t h e g a p r a n g e 4 - 5 0 m m .
1 8
2
2
THE WIGGLER W61
Fig. 8: U n d u l a t o r U 2 4 : M a g n e t i c array a n d flexible taper ( w a t e r c o o l e d ) inside t h e v a c u u m v e s s e l .
(Fig. 8).
.JJ24
I
at 8 mm,
B = 0.644
T, 240 x 54 ¡xrad?
T h e w i g g l e r W 6 1 , n o w in routine o p e r a t i o n at t h e M S
b e a m l i n e , h a s b e e n d e s i g n e d for m a x i m u m horizontal
flux density in t h e e n e r g y r a n g e 5 - 4 0 keV. A m a x i m u m
field at a s h o r t p e r i o d (61 m m ) h a d to b e a c h i e v e d . T h e
w i g g l e r h a s b e e n built a n d magnetically m e a s u r e d by
D A N F Y S I K . PSI w a s r e s p o n s i b l e for t h e electrical part
of ID a n d control s y s t e m . It presently o p e r a t e s at a m i n i m u m g a p of 11.5 m m u s i n g a small g a p v a c u u m c h a m ber (Al, 8 m m a p e r t u r e ) built by A P S . Later a f i x e d - g a p
c h a m b e r ( a p e r t u r e 5 m m ) will b e installed to allow a
m i n i m u m g a p of 8 m m a n d a m a g n e t i c field of 1.85 T.
B e c a u s e of t h e high field at small g a p s , t h e m a g n e t i c
1.5*10
10
11
12
Energy
13
14
[keV]
Fig. 9: M e a s u r e d spectral flux of t h e U 2 4 i n - v a c u u m
u n d u l a t o r at 8 m m m a g n e t i c g a p . F r o m t h e c e n t e r e n e r g y a n d w i d t h of t h e 9th a n d 11th h a r m o n i c , t h e electron b e a m e n e r g y a n d e n e r g y s p r e a d is d e t e r m i n e d as
2.44(2) G e V a n d 0.17 - 0 . 2 1 % respectively.
T h e m a g n e t structure, built a n d m e a s u r e d by
S P r i n g - 8 , is a hybrid s t r u c t u r e with 5 7 p e r i o d s of 2 4
m m . U s i n g N d F e B m a g n e t m a t e r i a l , a field of 0.83 T
is r e a c h e d at t h e p r e s e n t m i n i m u m g a p of 6.5 m m . At
8 m m g a p , a m a g n e t i c t a p e r < 2 G (i.e. m e c h a n i c a l g a p
t a p e r < 2 ¿¿m) h a s b e e n m e a s u r e d . T h e p h a s e error
is < 2 . 5 ° for t h e relevant g a p r a n g e 6.5-20 m m . T h e
vertical a n d horizontal first integrals, m e a s u r e d with a
flip coil, a r e w i t h i n ± 2 5 G - c m in a ± 2 0 m m horizontal
region. T h e m e a s u r e d c l o s e d orbit distortion is s m a l l ,
< 1 0 ¿¿ni (rms) ( < 3 ¿¿m (rms)) before (after) c o m p e n s a tion in both p l a n e s for t h e g a p r a n g e 6.5-38 m m . T h e
lifetime at low (40 m A ) a n d high (200 m A ) c u r r e n t is not
affected, it e v e n i n c r e a s e s at small g a p s .
THE UNDULATOR U17 (IN-VACUUM)
T h e s u c c e s s of t h e U 2 4 o p e r a t i o n h a s resulted in t h e
l a u n c h i n g of t h e p r o d u c t i o n of t w o n e w i n - v a c u u m u n dulators, e a c h 2 m long. T h e hybrid u n d u l a t o r s with a
Fig. 10: T h e s h o r t p e r i o d w i g g l e r W 6 1 installed at t h e
S L S s t o r a g e ring. Two m o t o r i z e d a x e s a r e u s e d to
m o v e t h e m a g n e t i c arrays. T h e small g a p ID v a c u u m
c h a m b e r ( a p e r t u r e 8 m m ) is rigidly m o u n t e d o n t w o
c o l u m n s to allow a n a l i g n m e n t b e l o w 0.1 m m .
63
|W61
g
-100
^
j
^
7.5mm
11mm
~ > -15mm
^
^
-200
-20
-10
0
x [mm]
10
20
F i g . 12: Vertical a n d horizontal field integrals in t h e
region ± 2 0 m m horizontally, m e a s u r e d for t h e w i g g l e r
W 6 1 at o p e r a t i n g g a p s of 7.5 m m , 11 m m a n d 15 m m
(remark: A n arbitrary dipole offset is u s e d in t h e f i g u r e
to d i p l a c e t h e g r a p h s for clarity
REFERENCES
[1] G. Ingold, T. S c h m i d t , Insertion Devices for SLS,
PSI Scientific R e p o r t 1 9 9 9 , Vol. II; G. Ingold,
T. S c h m i d t , Photon Sources Based on Insertion
Devices at SLS, PSI Scientific R e p o r t 2 0 0 0 , Vol. V I I .
F i g . 11 : W i g g l e r W 6 1 : G a p o p e n position. A lead shield
p r o t e c t s t h e linear e n c o d e r for t h e g a p reading a g a i n s t
possible radiation d a m a g e .
s h i m m i n g of t h e d e v i c e w a s a c h a l l e n g i n g task. For t h e
relevant g a p r a n g e of 7.5 - 15 m m , t h e m e a s u r e d first
field integrals a r e within t h e s p e c i f i e d limits for t h e reg i o n ± 1 5 m m horizontally a n d e x c e e d t h e limits slightly
c l o s e to ± 2 0 m m (Fig. 12). In t h e g a p r a n g e 1 2 - 1 5 0 m m
t h e c l o s e d orbit distortion m e a s u r e d before (after) c o m p e n s a t i o n is < 5 0 í¿m (rms) ( < 1 5 ¿¿m ( r m s ) ) . T h e vertical t u n e shift is A Q = 0 . 0 0 3 5 at 12 m m gap. Effects o n
t h e lifetime a r e not o b s e r v e d .
[2] C. S c h u l z e - B r i e s e et al., Commissioning
tein Crystallography
beamline X06SA,
tific R e p o r t 2 0 0 1 , V I I .
[3] B. Patterson et al., The Materials
PSI Scientific R e p o r t 2 0 0 1 , V I I .
Science
of the ProPSI S c i e n -
beamline,
[4] L. Patthey et al., Status of the Surface and Interface: Spectroscopy
beamline, PSI Scientific R e p o r t
2 0 0 1 , VII.
[5] U. F l e c h s i g , G. Ingold, R. K r e m p a s k a , J . K r e m pasky,
F. Nolting, L. Patthey, C. Q u i t m a n n ,
T. S c h m i d t , The Surface/Interface:
Microsciopy;
Beamline, PSI Scientific R e p o r t 2 0 0 1 , V I I .
y
SUMMARY
In 2 0 0 1 five IDs h a v e b e e n installed at t h e S L S s t o r a g e
ring. No effects o n t h e lifetime h a v e b e e n o b s e r v e d
for g a p s a s low a s 6.5 m m . C l o s e d orbit d i s t o r t i o n s
i n d u c e d by m a g n e t i c field c h a n g e s in t h e IDs a r e c o m p e n s a t e d by f e e d f o r w a r d local c o r r e c t i o n coils, with a
residual b e a m m o t i o n b e l o w I 5 ^ m . Together with t h e
s l o w orbit f e e d b a c k all IDs a r e t r a n s p a r e n t to t h e elect r o n b e a m . T h e elliptical u n d u l a t o r U E 5 6 / 2 a n d t h e chic a n e s y s t e m will b e installed in s u m m e r 2 0 0 2 . W o r k o n
t h e next p h a s e of I D - c o n s t r u c t i o n h a s s t a r t e d , n a m e l y
t w o i n - v a c u u m u n d u l a t o r s a n d o n e S a s a k i / A P P L E II
t y p e elliptical undulator.
[6] W. B u l g h e r o n i , T. K o r h o n e n , C. Vollenweider, G. Ing o l d , T. S c h m i d t , Insertion Devices:
Control Hardware, PSI Scientific R e p o r t 2 0 0 1 , V I I .
[7] T. K o r h o n e n , B. Kalantari, W. B u l g h e r o n i , C. Vollenweider, G. Ingold, T. S c h m i d t , Insertion
Devices:
Computer Control, PSI Scientific R e p o r t 2 0 0 1 , V I I .
[8] M. B ö g e , T. Schilcher, Beam Position
Stabilization,
PSI Scientific R e p o r t 2 0 0 1 , V I I .
[9] S. H a s h i m o t o , S. S a s a k i , Concept of a New Undulator that will Suppress
the Rational
Harmonics,
Nucl. Instr. a n d M e t h o d s A 3 6 1 , 1995.
64
INSERTION DEVICES: CONTROL HARDWARE
W. Bulgheroni,
T. Korhonen,
In the past two years an ID drive and control
to operate
stepper
incremental
encoders.
of one micron
magnetic
motors
during continuous
energy and polarization
for local control
the
several
is designed
tons. For elliptically
operation
G. Ingold,
has been developed
in open
to operate
gap and shift movements
scans as required
and to monitor
in EPICS,
system
loop and servo-motors
The drive system
forces reaching
implemented
in open
C. Vollenweider,
Schmidt
that uses a flexible
or closed
loop (feedback)
up to 8 axes synchronously
in the presence
polarized
user applications.
according
to industrial
the systems
A Programmable
safety
standards.
ring and for the control
architecture
with
with a
of highly non-linear,
undulators,
for specific
used for the control of the storage
T.
allows
linear
precision
non-uniform
continuous
Logic Unit is used
The remote
control
of the monochromators
is
in
beamlines.
ID E L E C T R I C A L C A B I N E T
INTRODUCTION
T h e m a g n e t i c field of a p e r m a n e n t m a g n e t (pm) inser-
o
Motor Control
:
tion d e v i c e (ID) is t u n e d by t h e m e c h a n i c a l m o v e m e n t
of several m a g n e t a r r a y s in t h e p r e s e n c e of highly n o n -
ÜX4S C ütlttol :
:
linear, n o n - u n i f o r m m a g n e t i c f o r c e s of several t o n s :
Displav
• Planar I D s ( h y b r i d / p p m t y p e ) : vertical m o v e m e n t of
a r r a y s for t h e g a p c h a n g e (i.e. t h e c h a n g e of t h e p h o ton energy).
• Elliptical I D s ( S a s a k i / A P P L E II t y p e ) : in addition to t h e
g a p c h a n g e t h e r e is t h e longitudinal 'shift' m o v e m e n t of
t h e m a g n e t a r r a y s (i.e. t h e c h a n g e of t h e p h o t o n polarization).
F i g . 1 : Layout of t h e c o n t r o l s y s t e m for t h e insertion
d e v i c e s installed at t h e S L S .
B e s i d e s t h e p r e c i s i o n r e q u i r e d , t h e ID d r i v e s y s t e m
h a s to b e reliable a n d safe a c c o r d i n g to industrial s t a n dards.
either s t e p p e r m o t o r s or s e r v o - m o t o r s , h a v e to o p e r a t e
synchronuously.
4 - A x i s D r i v e : In c a s e of a n elliptical undulator, 4 a x e s
Permanent Magnet Devices
a r e o p e r a t e d s y n c h r o n o u s l y in t h e f e e d b a c k m o d e to
For w i g g l e r s a positional p r e c i s i o n of ~ 1 0 ¿¿m is usually
allow for flexible e n e r g y a n d polarization s c a n s .
sufficient, w h e r e a s for t u n a b l e u n d u l a t o r s a p r e c s i s i o n
8 - A x i s D r i v e : U s i n g a 7 - m a g n e t c h i c a n e , t h e elliptical
of a few m i c r o n s is r e q u i r e d . Electrical m o t o r s a r e u s e d
twin-undulators UE56/1 and UE56/2 can be operated
for t h e m o v e m e n t of t h e m a g n e t arrays. T h e d r i v e s y s -
either in t h e ' c h i c a n e m o d e ' for fast polarization s w i t c h -
t e m a n d control d e v e l o p e d for IDs installed at t h e S L S
ing or in t h e ' p h a s e m a t c h e d m o d e ' , w h e r e b o t h u n d u -
ID's [1] is d e s i g n e d for flexibility a n d a l l o w s - b a s e d o n
lators a r e c o u p l e d to o n e d e v i c e . In t h e ' p h a s e m a t c h e d
a c o m m o n a r c h i t e c t u r e a n d d e p e n d i n g o n t h e specific
m o d e ' 8 - a x e s h a v e to b e o p e r a t e d s y n c h r o n o u s l y in t h e
requirement - two options:
feedback mode.
• T h e u s e of s t e p p e r m o t o r s o p e r a t e d in o p e n loop.
P r g r a m m a b l e L o g i c C o n t r o l : T h e e s s e n t i a l part of t h e
• T h e u s e of s e r v o - m o t o r s o p e r a t e d in o p e n or c l o s e d
ID c o n t r o l is t h e P L C unit ( S i m a t i c - S 7 / 3 0 0 S P S ) . It h a s
loop ( f e e d b a c k ) .
several f u n c t i o n s :
T h e basic d e s i g n of t h e c o n t r o l s y s t e m is d e s c r i b e d
m o v e m e n t of 2 c o u p l e d a x e s , (2) t h e local c o n t r o l , (3)
by [2]:
t h e limit s w i t c h c o n t r o l , (4) t h e e m e r g e n c y s t o p ( m e -
M o t o r s : Stepper motors and servo-motors, manufac-
c h a n i c a l h a r d w a r e protection) a n d (4) t h e c o m m u n i -
t u r e d by S I G - P o s i t e c h / B e r g e r L a h r . B o t h t y p e s u s e b a -
c a t i o n to t h e higher level ( r e m o t e ) c o m p u t e r c o n t r o l
(1) t h e a x e s control ( s y n c h r o n o u s
sically t h e s a m e p o w e r amplifier unit (Twin-Line S e r i e s )
(VME/VXworks/EPICS).
w h i c h a l l o w s a c o m m o n d e s i g n for t h e m o t o r c o n t r o l .
Axes control:
Linear
P L C control unit: L a g error d e t e c t i o n a n d s y n c h r o n i z -
Encoders
Incremental
linear
encoders
are
Critical safety f e a t u r e realized by t h e
u s e d for t h e g a p ( H e i d e n h a i n U L S 3 0 0 C w i t h r e a d - o u t
ing error d e t e c t i o n d u r i n g t h e o p e r a t i o n of t w o c o u p l e d
e l e c t r o n i c s E X E 9 3 2 ) a n d shift ( H e i d e n h a i n L S 4 0 6 C
axes.
w i t h r e a d - o u t e l e c t r o n i c s E X E 4 0 6 C ) position c o n t r o l .
shift m o v e m e n t a r e i m m e d i a t e l y s t o p p e d a s s o o n a s
To prevent m e c h a n i c a l d a m a g e , t h e g a p - a n d
T h e position s i g n a l s a r e directly t r a n s f e r r e d to t h e V M E
p r e s e t limit v a l u e s a r e e x c e e d e d . For error c o r r e c t i o n ,
c r a t e v i a t h e IK342 b o a r d ( H e i d e n h a i n ) .
t h e a x e s control b e c o m e s d i s a b l e d to allow s i n g l e a x i s
D r i v e A x i s : A drive a x i s ( g a p or shift m o v e m e n t ) c o n -
adjustments.
sists of o n e m o t o r including a rotary e n c o d e r , o n e b r a k e
a n d o n e linear e n c o d e r ( i n c r e m e n t a l ) .
2-Axis Drive:
B o t h t h e g a p ( e n e r g y c h a n g e ) a n d t h e shift m o t i o n (polarization c h a n g e ) a r e a c t i v a t e d by 2 a x e s . B o t h m o t o r s ,
R e m o t e C o n t r o l : T h e ID c o m p u t e r control [3] is b a s e d
o n E P I C S a n d is also u s e d for t h e c o n t r o l of t h e b e a m lines a n d t h e a c c e l e r a t o r s y s t e m s . E a c h ID is e q u i p p e d
65
drive s y s t e m ) . R e m o t e control v i a V M E / E P I C S / O M S ,
a x e s control is active. (5) S c a n n i n g m o d e : a s (4), but
t h e g a p - a n d shift a x e s a r e m o v e d c o n t i n u o u s l y over a
w i d e r a n g e (the r a n g e is s u b d i v i d e d in small intervalls
s t o r e d in t h e O M S - c o n t r o l l e r c a r d ) .
V e l o c i t y C o n t r o l : R o t a r y e n c o d e r s (incremental) o n
t h e m o t o r s a r e u s e d for t h e m o t o r velocity control (feedb a c k m o d e ) by t h e m o t o r amplifier unit.
P o s i t i o n C o n t r o l : T h e g a p - a n d shift position is m e a s u r e d a n d c o n t r o l l e d in a r e d u n d a n t w a y : (1) T h e (inc r e m e n t a l ) rotary e n c o d e r s i g n a l s f r o m t h e m o t o r s a r e
u s e d for t h e position control by t h e P L C unit. (2) T h e
h i g h - r e s o l u t i o n linear (incremental) e n c o d e r s a r e u s e d
for t h e position control v i a V M E / E P I C S / O M S .
L i m i t S w i t c h e s : (1) M i n / M a x limit s w i t c h e s for t h e g a p a n d s h i f t - m o v e m e n t , r e a d by t h e m o t o r p o w e r amplifier
unit a n d t h e P C L control unit. (2) H o m e limit s w i t c h e s ,
c o n t r o l l e d by t h e P L C , u s e d for referencing t h e linear
e n c o d e r s . (3) Interlock limit s w i t c h e s , c o n t r o l l e d by t h e
P L C , u s e d by t h e m a c h i n e safety interlock s y s t e m . (4)
C h a m b e r protection s w i t c h e s , c o n t r o l l e d by t h e P L C ,
u s e d to prevent a collision b e t w e e n m a g n e t arrays a n d
the vacuum chamber.
Electromagnetic Devices
F i g . 2: Electrical c a b i n e t for a 4 - a x e s ID drive a n d c o n trol (elliptical u n d u l a t o r U E 5 6 ) . Left side: T o u c h p a n n e l
(top), P L C (middle) a n d m o t o r amplifier units ( b o t t o m ) .
Right side: V M E c r a t e (top), g a p a n d shift reading display (middle, not yet installed) a n d E X E - b o x e s for t h e
linear e n c o d e r s (bottom).
with t w o V M E c r a t e s o p e r a t i n g u n d e r V X w o r k s . T h e
O M S 5 8 m o t o r controller c a r d ( O r e g o n M i c r o s y s t e m s ) is
u s e d to o p e r a t e u p to 8 m o t o r s , either s t e p p e r or s e r v o
m o t o r s , a n d u p to 8 linear e n c o d e r s v i a t h e 8 - c h a n n e l
O M S - I 0 5 8 input/output c a r d .
O p e r a t i o n M o d e s : (1) S e t - u p m o d e : local control v i a
t h e P L C control unit. U s e d for t h e a d j u s t m e n t of a single a x i s to c o r r e c t t h e lag a n d s y n c h r o n i z i n g error of t w o
c o u p l e d a x e s (axes control not active). A l s o u s e d for
referencing t h e linear e n c o d e r s . (2) M a n u a l m o d e : a s
(1 ), but t h e a x e s control is active ( c o u p l e d a x e s a r e o p e r a t e d s y n c h r o n o u s l y ) . (3) M i c r o - s t e p m o d e : local c o n trol v i a V M E / E P I C S / O M S . T h e a x e s control is active.
G a p - a n d shift c h a n g e s in 1 /xm, 10 /xm a n d 100 /xm
intervalls, u s e d for m a g n e t i c m e a s u r e m e n t s , for alignm e n t a n d for t h e a d j u s t m e n t of limit s w i t c h e s . (4) S t o p
- a n d G o m o d e : g a p - a n d shift c h a n g e s in small intervalls (also in s y n c h r o n i s m with t h e m o n o c h r o m a t o r
T h e e l e c t r o m a g n e t i c elliptical t w i n - u n d u l a t o r s U E 2 1 2 / 1
a n d U E 2 1 2 / 2 a r e f i x e d - g a p d e v i c e s . Instead of a m e c h a n i c a l m o v e m e n t of m a g n e t i c arrays, t h e m a g n e t i c
field is t u n e d v i a D C c u r r e n t s . By properly a d j u s t i n g
t h e c u r r e n t in t h e vertical a n d horizontal iron poles, t h e
d e v i c e s c a n b e o p e r a t e d in t h e linear/circular polarization m o d e a n d in t h e p e r i o d i c / q u a s i p e r i o d i c field m o d e .
For t h e vertical (horizontal) field, 2 (1 ) m a i n p o w e r s u p plies of 145 A / 7 5 V ( ± 1 2 0 A / 6 0 V) a r e u s e d . In a d dition, t r i m c u r r e n t s a r e a p p l i e d to c o r r e c t for s t e e r i n g
a n d multipole errors. Including t h e p o w e r s u p p l i e s for
t h e 7 - m a g n e t c h i c a n e , 3 7 digital p o w e r s u p p l i e s h a v e
to b e c o n t r o l l e d [4]. T h e p o w e r supplies, built by P S I ,
a r e t h e s a m e a s for all t h e S L S m a g n e t s [5]. To c o n trol hysteresis a n d end-field c o m p e n s a t i o n effects for
reproducible field settings, all ID p o w e r s u p p l i e s track
e a c h other d u r i n g a field ramp.
REFERENCES
[1] G. Ingold, T. S c h m i d t , Insertion Devices installed at
the SLS (Phase I), PSI Scientific R e p o r t 2 0 0 1 , V I I .
[2] W. B u l g h e r o n i , P. Perren,
vice Pflichtenheft:
Undulator
Dezember 2000.
SLS - Insertion
DeUE56, T M - 9 3 - 0 0 - 1 0 ,
[3] T. K o r h o n e n , B. Kalantari, W. B u l g h e r o n i , C. Vollenweider, G. Ingold, T. S c h m i d t , Insertion
Devices:
Computer Control, PSI Scientific R e p o r t 2 0 0 1 , V I I .
[4] A. L u e d e k e et. al., Digital Power Supplies
for the
Swiss Light Source, I C A L E P S C S 2 0 0 1 , S a n J o s e ,
California, U S A .
[5] F. J e n n i , M. Horvat, L. Tanner, Precision of the SLS
Power Supplies, PSI Scientific R e p o r t 2 0 0 0 , V I I .
66
CONCEPTUAL DESIGN: SUB-PICOSECOND HARD X-RAY SOURCE
G. Ingold, A. Streun,
B. Singh, R. Abela, P. Beaud, D. Grolimund, G. Knopp, L. Rivkin,
T. Schmidt, H. Sigg, J.F. van der Veen, A. Wrulich
S. Khan (BESSY, Berlin)
V. Schlott,
We propose to develop at the SLS a facility for sub-picosecond
X-ray pulses based on an
electron-beam
slicing method based on the characteristics
of the U17 as the radiator. The undulator is foreseen to be the
one planned for the micro-XAFS/diffraction
beamline.
The facility will enable time-dependent
studies of the
structural dynamics of condensed matter and photochemistry
and will complement
time resolved studies in
the pico- and nanosecond
range planned at the photoelectron-microscopy
beamline for soft X-rays.
INTRODUCTION
T h e e l e c t r o n - b e a m slicing m e t h o d , recently d e m o n s t r a t e d [1] at t h e A L S , Berkeley, is b a s e d on t h e p h y s i c s
of a s e e d e d low-gain F E L . T h i s p h y s i c s is k n o w n for 2 0
y e a r s . T h e slicing m e t h o d t a k e s a d v a n t a g e of m o d e r n
ultrafast optical lasers to p r o d u c e a s u b - p i c o s e c o n d
e l e c t r o n b u n c h of low c h a r g e in a s t o r a g e ring. T h e
laser interacts with t h e e l e c t r o n b e a m in a w i g g l e r
('modulator'), resonantly t u n e d to t h e laser w a v e l e n g t h .
In a d i s p e r s i v e s e c t i o n , t h e e n e r g y m o d u l a t e d e l e c t r o n s
originating f r o m t h e l a s e r / e - b e a m interaction region bec o m e spatially s e p a r a t e d to p r o d u c e a s u b - p i c o s e c o n d
X-ray p u l s e in t h e 'radiator' ( b e n d i n g m a g n e t or u n d u lator). H e n c e ultrafast optical lasers c a n b e u s e d to
e x t e n d optical s t u d i e s to include X-ray t e c h n i q u e s s u c h
a s X-ray a b s o r p t i o n s p e c t r o s c o p y (for local c h e m i c a l
a n d m a g n e t i c information) a n d X-ray diffraction (for
structural information), with t i m e resolution b e l o w
100 fs. A t o m i c resolution with 100 fs p u l s e s is a c h i e v e d
with h a r d X - r a y s (10 keV) rather t h a n with soft X - r a y s
(1 keV).
To start e x p e r i m e n t s in this r e g i m e , t h e c o n s t r u c tion of a s u b - p i c o s e c o n d undulator radiation ( S P U R )
s o u r c e for h a r d X - r a y s ( 1 0 0 fs, 5-17 k e V ) , b a s e d o n
t h e l a s e r / e - b e a m slicing ( L E B S ) is p r o p o s e d [2, 3].
T h e e x p e c t e d a v e r a g e flux a n d brilliance u s i n g a 5 k H z
laser is given in Figure 6. S u c h a s o u r c e w o u l d b e
s u p e r i o r to existing s o u r c e s ( L a s e r P l a s m a S o u r c e ,
T h o m p s o n / C o m p t o n Scattering, LEBS using bending
m a g n e t radiation) in t e r m s of p u l s e l e n g t h , tunability,
a v a r a g e flux a n d a v e r a g e brilliance.
C o m p a r e d to
f u t u r e 4th g e n e r a t i o n light s o u r c e s ( S A S E X - R a y F E L ,
E R L / P E R L ([Photo-injected] E n e r g y R e c o v e r y Linac),
t h e p r o p o s e d facility is a low p e r f o r m a n c e X-ray s o u r c e .
It is an i n t e r m e d i a t e s t e p t o w a r d s 4 t h g e n e r a t i o n X-ray
user facilities (both in t e r m s of t h e d e v e l o p m e n t a n d
t h e u s e of s u c h s o u r c e s ) , w h i c h m a y b e c o m e available
at t h e e n d of this d e c a d e .
SUB-PICOSECOND X-RAY SOURCE
For t h e c o n s t r u c t i o n of a S P U R b e a m l i n e b a s e d o n
L E B S , t h e S L S s t o r a g e ring offers several a d v a n t a g e s :
(1) T h e b e a m e n e r g y of 2.4 G e V is low e n o u g h for a n
e n e r g y m o d u l a t i o n of at least 0 . 5 % u s i n g a m o d e r n
f e m t o s e c o n d laser s y s t e m (800 n m , 5 0 fs, 1 m J / p u l s e ,
1-5 k H z ) . (2) T h e b e a m e n e r g y is high e n o u g h to
p r o d u c e sufficient h a r d X - r a y s u p to 17 keV by t h e
u s e of higher u n d u l a t o r h a r m o n i c s (11th/13th) in t h e
radiator. (3) Instead of u s i n g t w o s e c t o r s s e p a r a t e d
by an a c h r o m a t i c arc s e c t i o n , t h e S P U R s o u r c e will
b e installed in o n e long straight s e c t i o n (5L, 11 m ) .
T h i s p r o v i d e s t h e s m a l l e s t t e m p o r a l s t r e t c h i n g of t h e
e l e c t r o n b u n c h slice (due to t h e n o n - i s o c h r o n i c i t y of
t h e S L S s t o r a g e ring) a n d t h u s t h e s h o r t e s t X-ray
p u l s e s ( < 100 fs). (4) T h e low e m i t t a n c e optics allows
t h e installation of a p p r o p r i a t e small g a p , s h o r t p e r i o d
w i g g l e r s a n d u n d u l a t o r s ( i n - v a c u u m ) to m a t c h t h e
required radiation c h a r a c t e r i s t i c s .
T h e S P U R s o u r c e s h o w n in Figure 1, c o n s i s t s of
t h e f e m t o s e c o n d optical laser s y s t e m (high repetition
rate, high a v e r a g e p o w e r ) , t h e m o d u l a t o r (wiggler), t h e
d i s p e r s i v e s e c t i o n ( c h i c a n e ) , a n d t h e radiator (undulator). It will b e installed in sector 5 a s a n e x t e n s i o n to
t h e h a r d X-ray /xXAS b e a m l i n e . A basic optical layout
of t h e s o u r c e that leaves t h e non-linear b e a m d y n a m ics basically u n c h a n g e d h a s b e e n f o u n d .
Dynamic
a p e r t u r e c a l c u l a t i o n s indicate compatibility with t h e
g e n e r a l m a c h i n e p e r f o r m a n c e [4]. A 4 - m a g n e t c h i c a n e
a d j a c e n t to t h e m o d u l a t o r p r o v i d e s a vertical d i s p e r s i o n
of 8.8 m m at t h e radiator, resulting in a 5<r t r a n s v e r s e
spatial s e p a r a t i o n (48 /xm) of t h e sliced e l e c t r o n s f r o m
t h e c o r e b e a m . S u b - p i c o s e c o n d (~ 2 0 0 fs) radiation
200 fs X-ray/IR
Diagnostic
Fig. 1 : T h e w i g g l e r (modulator) w i t h a vertical 4m a g n e t c h i c a n e a n d t h e small g a p u n d u l a t o r (radiator) a r e installed in o n e straight s e c t i o n . A q u a d r u p o l e
triplet splits t h e long straight s e c t i o n 5 L into t w o s h o r t
straights to install t w o small g a p IDs.
will b e available also at t h e c e n t e r b e n d i n g m a g n e t
B X - 0 5 in t h e arc s e c t i o n i m m e d i a t e l y d o w n s t r e a m of
s e c t o r 5 L . T h e diagnostic b e a m l i n e u n d e r c o n s t r u c t i o n
at B X - 0 5 will exploit t h e c o h e r e n t IR radiation e m i t t e d
by t h e sliced e l e c t r o n b u n c h to m o n i t o r relevant s o u r c e
parameters such as the pulse length, the time structure
a n d t h e laser s y n c h r o n i z a t i o n .
In a s e c o n d B X - 0 5
67
outlet, s u b - p i c o s e c o n d X-ray p u l s e s will b e available
o n e order of m a g n i t u d e less in intensity c o m p a r e d to
the SPUR source.
\
a.
%
0.01
0.008
0.006
0.004
Design Parameters
0.002
T h e p r e s e n t c o n c e p t u a l d e s i g n of t h e S P U R s o u r c e is
b a s e d on t h e following p a r a m e t e r s :
• T k s a p p h i r e l a s e r : 8 0 0 n m ( f u n d a m e n t a l ) , 18 optical
c y c l e s , 5 0 fs [ F W H M ] , 1 m J / p u l s e , 5 W, 5 k H z .
• M o d u l a t o r : small g a p , s h o r t p e r i o d w i g g l e r W 1 1 0
0
l l l l l i i
-0.002
-0.004
-0.006
-0.008
-0.01
0.3
-0.2
—i i i i
-0.1
i
i i
i
i
i
i i i i
0.1
0.2
LASER: T I : S A P P H I R E
F i g . 3: C a l c u l a t e d m o m e n t u m a n d spatial distribution of
t h e electron b u n c h following interaction with t h e laser
in t h e modulator. A n e n e r g y m o d u l a t i o n > 0 . 5 % is required.
1 ST H A R M O N I C
WAVELENGTH A I
800 N M
ENERGY/PULSE A ¿
1 (3)
PULSE LENGTH tl
NO. OPTICAL CYCLES
0.3_
x 10
z / m
MJ
50 FS
M
18
L
REPETITION RATE F¿
1-5 K H Z
(PHASE 1 )
5 - 1 0 KHZ
(PHASE 2)
ENERGY M O D U L A T I O N A E :
MODULATOR W H O
>
12 M E V
(= 5
a)
E
F i g . 2: L a s e r p a r a m e t e r s .
(possibly i n - v a c u u m ) , r e s o n a n t to t h e laser f u n d a m e n tal, p e r i o d 110 m m , g a p 7.5 m m , p e a k field 2.5 T,
K-parameter 25.6, length 2 m, n u m b e r of p e r i o d s 18
( m a t c h e d to t h e n u m b e r of optical laser c y c l e s ) .
• R a d i a t o r : small gap, s h o r t p e r i o d undulator U 1 7 (inv a c u u m ) , p e r i o d 17 m m , g a p 4 m m , p e a k field 1 T, X-ray
e n e r g y r a n g e 5-17 k e V ( 3 . - 1 1 . h a r m o n i c ) , length 2 m,
n u m b e r of p e r i o d s 117.
• C h i c a n e : 4 - m a g n e t c h i c a n e , length 0.3 m, field
0.43 T, vertical d i s p e r s i o n 8.8 m m . T h e vertical disp l a c e m e n t of t h e s t o r e d b e a m in t h e m o d u l a t o r is u s e d
to s e p a r a t e a n d block t h e high p o w e r wiggler radiation.
• E n e r g y m o d u l a t i o n : A E > 12 M e V (0.5%), laser
energy 1 mJ/pulse.
• S l i c i n g e f f i c i e n c y : 5 . 5 x l 0 ~ (5 k H z , 4 0 0 b u n c h e s ) ,
d e f i n e d a s t h e n u m b e r of e l e c t r o n s with
AE
> 0 . 5 % / s e c o n d / b e a m c u r r e n t (400 m A ) . By
n u m e r i c a l integration w e c a l c u l a t e AE
=
—efv±E(x, t)dt w h e r e v± is t h e electron t r a n s v e r s e velocity
a n d E(x, t) t h e electrical field of t h e laser. T h e waist of
t h e laser b e a m at t h e c e n t e r of t h e m o d u l a t o r is typically 2 0 0 /im (H) x 2 0 0 ixm (V) (see Figure 3).
undulator h a r m o n i c s ( U 2 4 undulator ( i n - v a c u u m ) , currently installed at t h e P X - b e a m l i n e [6]).
• B a c k g r o u n d s u p p r e s s i o n : (i) A c h o p p e r c l o s e to t h e
i n t e r m e d i a t e i m a g e of t h e s o u r c e is u s e d to m a t c h t h e
duty c y c l e of t h e X-ray b e a m to t h e laser s y s t e m , (ii)
G a t e d ( ~ 2 ns) d e t e c t o r s have to b e u s e d to s u p p r e s s
b a c k g r o u n d X - r a y s v i a "laser o n / laser off" difference
m e a s u r e m e n t s (on individual p u l s e s ) .
Laser System
T h e f e m t o s e c o n d optical laser s y s t e m will s e r v e dual
p u r p o s e of providing laser p u l s e s for slicing a s well a s
(tunable) " p u m p " p u l s e s for s a m p l e excitation. Initial exp e r i m e n t a l e x p e r i e n c e with t h e s u b - p i c o s e c o n d X-ray
s o u r c e c a n b e g a i n e d with a reliable c o m m e r c i a l s y s t e m ( p h a s e 1 ). W e e x p e c t that a 5 0 fs T i : s a p p h i r e laser
s y s t e m b a s e d on t h e c h i r p e d p u l s e amplification [5]
with an a v e r a g e p o w e r of 3 W (1 m J / p u l s e , 3 k H z ) will
c o m m e r c i a l l y b e available at t h e e n d of y e a r 2 0 0 1 . T h e
d e s i g n of this laser s y s t e m shall allow an u p g r a d e in
t e r m s of p u l s e e n e r g y a n d repetition rate ( p h a s e 2 ) .
For t h e u p g r a d e , a s y s t e m will be d e v e l o p e d deliver-
9
• P u l s e s e p a r a t i o n : (i) Spatial s e p a r a t i o n , 4 8 iim, 5as e p a r a t i o n (vertical) in t h e radiator (separation of t h e
sliced e l e c t r o n s f r o m t h e c o r e b e a m ) ; 1.3:1 d e m a g nified i n t e r m e d i a t e i m a g e of t h e s o u r c e in t h e b e a m line; spatial s e p a r a t i o n of t h e s u b - p i c o s e c o n d X-ray
p u l s e s with a pair of slits d i s p l a c e d 5a a b o v e t h e o p tical axis, (ii) S e p a r a t i o n in e n e r g y : t h e s u b - p i c o s e c o n d
X - r a y s a r e blue-shifted in e n e r g y with respect to t h e
h a r m o n i c energy. For t h e 7th (11th) h a r m o n i c t h e s u p p r e s s i o n of t h e l o n g - p u l s e X-ray flux is e s t i m a t e d to be
2 x 1 0 ( 2 x 1 0 ) , b a s e d o n t h e m e a s u r e m e n t of higher
_ 2
_ 1
50 fs
100 MHz/1 nJ
200 ps
100MHz/100pJ
200 ps
1 kHz/ 1.5 mJ
50 fs
1 kHz/1 mj
F i g . 4: F e m t o s e c o n d T k s a p p h i r e laser s y s t e m .
ing p u l s e s of 5 0 fs scalable in pulse e n e r g y to 3 m J
(to a c c o u n t for diffraction effects at t h e laser interaction
point) a n d in repetition rate to 10 k H z . S u c h a s y s t e m
c o u l d be b a s e d o n a d e s i g n s h o w n in Figure 5.
S u b - P i c o s e c o n d X-Ray Pulses
T h e S P U R s o u r c e is d e s i g n e d to deliver 100 fs, 810 k e V X-ray p u l s e s with a n a v e r a g e flux of 2 x 1 0 p h o t o n s / s e c / 0 . 1 % b w a n d a v e r a g e brilliance of
6
68
to compressor
1.5 m j / 1 0 kHz
Pump
F i g . 5:
S c h e m a t i c v i e w of t h e d o u b l e t w o - p a s s
T i : s a p p h i r e 10 k H z amplifier. P: polarizer; FR: Faraday
rotator.
5 x 10
1 0
p h o t o n s / s e c / m m / m r a d / 0 . 1 % b w . To c a l c u l a t e
2
2
Short Pulses: Hard X - Rays
Flux: F [ p h / s e c / 0 . 1 % bw]
2
2
Brilliance: B [ p h / s e c / m m / m r a d / 0 . 1 % bw]
N
hi/
[keV]
1
3
5
7
9
11
13
1.5
4.6
7.7
10.8
13.9
16.9
20.0
Flux
[100 fs,
5 kHz]
1.8E+7
6.5E+6
2.3E+6
8.0E+5
3.3E+5
1.3E+5
4.8E+4
Brilliance
[100 fs,
X-ray signal: spatial s e p a r a t i o n ( m a s k ) , s e p a r a t i o n
by e n e r g y ( m o n o c h r o m a t o r ) a n d s e p a r a t i o n in t i m e
(gating, "laser o n / l a s e r off" difference m e a s u r e m e n t s ) .
(5) Diagnostic t o o l s h a v e t o b e available to c h a r a c t e r i z e
b o t h t h e optical laser b e a m ( F E L g a i n , s y n c h r o n i z a t i o n )
a n d t h e s u b - p i c o s e c o n d X-ray p u l s e s ( f r o m c o h e r e n t
IR radiation).
(6) T h e c h i c a n e v a c u u m c h a m b e r
w h i c h c o n n e c t s t h e m o d u l a t o r a n d radiator v a c u u m
s y s t e m (including w a t e r - c o o l e d p h o t o n a b s o r b e r s to
block u n w a n t e d radiation), h a s to b e d e s i g n e d carefully.
For t h e S P U R s o u r c e to function at p e a k perform a n c e , several c o m p l e x s y s t e m s n e e d to o p e r a t e
s i m u l t a n e o u s l y including t h e laser s y s t e m ,
laser
s y n c h r o n i z a t i o n (~ 1-2 ps), t h e small g a p m o d u lator (possibly i n - v a c u u m ) , t h e i n - v a c u u m radiator
(operating o n higher h a r m o n i c s ) [6], diagnostic tools
a n d i n s t u m e n t a t i o n (autoVcross-correlator,
(X-ray)
streak camera, gated detectors) and the beamline
o p t i c s (chopper, c r y o g e n i c a l l y c o o l e d d o u b l e crystal
monochromator).
5 kHz]
3.5E+11
1.8E+11
7.0E+10
2.5E+10
9.0E+9
3.3E+9
1.2E+9
F i g . 6:
A v e r a g e flux a n d b r i g h t n e s s of t h e s u b p i c o s e c o n d X-ray p u l s e s for t h e U 1 7 u n d u l a t o r (integ r a t e d over 0.25 m r a d (H) x 0.05 m r a d (V)).
t h e a v e r a g e flux a n d b r i g h t n e s s , t h e laser slicing effic i e n c y h a s b e e n t a k e n into a c c o u n t a s well a s t h e red u c t i o n of b r i g h t n e s s d u e t o t h e u n d u l a t o r p h a s e error,
t h e e m i t t a n c e a n d t h e e n e r g y s p r e a d of t h e e l e c t r o n
beam.
Critical Issues
(1) T h e spatial s e p a r a t i o n of t h e sliced e l e c t r o n s f r o m
t h e c o r e b e a m n e e d s to b e o p t i m i z e d b e y o n d 5a
by i n c r e a s i n g t h e laser e n e r g y (to 3 m J ) a n d / o r t h e
d i s p e r s i o n of t h e c h i c a n e (both spatial a n d a n g u l a r
dispersion).
(2) T h e a v e r a g e s u b - p i c o s e c o n d X-ray
flux a n d brilliance is directly p r o p o r t i o n a l to t h e laser
repetition rate. T h e r e is a trade-off b e t w e e n backg r o u n d s u p p r e s s i o n a n d laser repetition rate (i.e. t h e
t i m e n e e d e d t o d a m p t h e b e a m halo) w h i c h m a y only
b e e v a l u a t e d experimentally. T h e laser s h o u l d h a v e
e n o u g h m a r g i n b o t h in p u l s e e n e r g y a n d repetition
rate. (3) For c r e a t i n g a c l e a n i n t e r m e d i a t e i m a g e of
t h e s o u r c e , t h e quality of t h e X-ray optics ( s p e c u l a r
reflections, s l o p e errors) will b e crucial. A p o s s i b l e
d e g r a d a t i o n of t h e spatial s e p a r a t i o n d u e to imperfect
X-ray o p t i c s n e e d s to b e e v a l u a t e d by ray tracing
calculations. (4) B e c a u s e t h e overall slicing efficiency
is v e r y low (~ 5-10E-9), several m e t h o d s n e e d to b e
a p p l i e d s i m u l t a n e o u s l y t o isolate t h e s u b - p i c o s e c o n d
T h e s o u r c e will b e c o n s t r u c t e d a l o n g
construction schedule (2002-2004).
a
3
year
REFERENCES
[1] R.W. S c h o e n l e i n , S. C h a t t o p a d h y a y , H.H. C h o n g ,
T.E. Glover, P.A. H e i m a n n , C.V. S h a n k , A.A. Z h o lents, M.S. Zolotorev, Generation
of
Femtosecond
Pulses of Synchrotron
Radiation,
SCIENCE 287
(2000) 2 2 3 7 a n d A p p l . Phys. B 71 (2000) 1.
[2] FEMTO-second
pulses of synchrotron
radiation at
the SLS, p r o p o s a l , F E M T O 1 2 . 0 1 . 0 1 , S L S , PSI Villigen, J a n u a r y 9, 2 0 0 1 a n d G. Ingold, T. S c h m i d t ,
Photon Sources based on Insertion Devices at SLS,
PSI Scientific R e p o r t 2 0 0 0 , V o l u m e V I I .
[3] G. Ingold, A. S t r e u n , B. S i n g h , R. A b e l a , P. B e a u d ,
G. K n o p p , L. Rivkin, V. Schlott, T. S c h m i d t , H. S i g g ,
J.F. v a n der V e e n , A. W r u l i c h ,
Sub-Picosecond
Optical Pulses at the SLS Storage Ring, Proc. PAC
2 0 0 1 , C h i c a g o , p. 2 6 5 6 a n d Proc. 2 1 s t ICFA B e a m
D y n a m i c s W o r k s h o p o n L a s e r - B e a m Interactions,
http://nslserver.physics.sunysb.edu/icfa/Papers/
collection.htm, W2-2.pdf
[4] A. S t r e u n , B. S i n g h , G. S i n g h , G. Ingold, V. Schlott,
Beam Dynamics Studies on an Extension of SLS for
Generation
of sub-picosecond
X-Ray Pulses, PSI
Scientific R e p o r t 2 0 0 1 , V o l u m e V I I .
[5] D. S t r i c k l a n d , G. M o u r o u , A p p l . Phys. B 5 8
(1985) 2 1 1 ; M. Pessot, P. M a i n e , G. M o u r o u ,
Opt. C o m m u n . 6 2 (1987) 4 1 9 ; P. M a i n e , D. Strickland, P. B a d o , M. Pessot, G. M o u r o u , I E E E
J. Q u a n t . Electron. 2 4 (1988) 3 9 8 .
[6] G. Ingold, T. S c h m i d t , Insertion Devices:
First Experiences,
PSI Scientific R e p o r t 2 0 0 1 , V o l u m e V I I .
69
INSERTION DEVICES: COMPUTER CONTROL
T. Korhonen,
B. Kalantari,
W. Bulgheroni,
C. Vollenweider,
G. Ingold, T.
Schmidt
In the initial phase of the Swiss Light Source, 5 (6) insertion devices (ID) have been installed [1] for the first
4 beamlines.
The control system for all the ID's follows, where possible, an uniform concept to allow a rapid
installation
and maintenance
schedule,
while at the same time allowing for a variety in operational
requirements. The components
of the control system include the gap drive system with encoders [2],
temperature
monitoring, beam position monitoring, power supply controllers
for corrector magnets [3] and a timing module [4]. The gap drive system requirements
range from micron-level
accuracy to driving double undulators
in
synchronism
with each other and also with the other beamline elements.
The control system is
implemented
in EPICS, using mostly readily available driver and device support modules plus standard
records.
Permanent Magnet Devices
T h e control of t h e m a g n e t array position is the centerpiece of a n insertion d e v i c e control s y s t e m . For the
W 6 1 w i g g l e r a n d t h e U E 5 6 p o l a r i z e d twin-undulator,
t h e control s y s t e m h a d to be d e v e l o p e d i n - h o u s e . A l t h o u g h the d e v i c e s are quite different, w e strived to find
a c o m m o n d e s i g n that c o u l d b e u s e d a s a b a s i s for f u ture d e v e l o p m e n t s .
Essentially the control c o n s i s t s of a drive s y s t e m to
m o v e the m a g n e t arrays vertically (gap, to c h a n g e the
p h o t o n e n e r g y ) a n d / o r longitudinally (shift, to c h a n g e
t h e p h o t o n polarization) including a position m e a s u r e m e n t s y s t e m to m o n i t o r the actual g a p a n d shift setpoints. T h e positions are typically m e a s u r e d by e n c o d e r s . T h e p h i l o s o p h y w a s to have a g a p m e a s u r i n g
d e v i c e a s c l o s e a s possible to t h e real m e c h a n i c a l gap.
To have a high precision over a large range, w e d e c i d e d to u s e linear i n c r e m e n t a l e n c o d e r s m a n u f a c t u r e d
by H e i d e n h a i n [6]. T h e s e l e c t e d e n c o d e r s ( U L S 3 0 0 )
have high-precision a b s o l u t e reference m a r k s . T h i s all o w s a high reproducibility of the g a p setting.
For the m o t o r controller w e s e l e c t e d to u s e the O r e g o n
M i c r o s y s t e m s O M S 5 8 m o t o r controller c a r d [9]. T h i s
c a r d h a d a g o o d s o f t w a r e s u p p o r t f r o m the E P I C S c o m munity a n d w a s already in u s e at S L S b e a m l i n e c o n trols. O n e big a d v a n t a g e w a s also that this c a r d h a s
s u p p o r t for b o t h s e r v o a n d s t e p p e r m o t o r s , with e s s e n tially the s a m e s o f t w a r e interface, so w e c o u l d u s e a
large part of the software for b o t h t h e s e r v o a n d stepper m o t o r - b a s e d s y s t e m s .
For the d e v e l o p m e n t of the g a p drive w e d e c i d e d to
build a n " I D - t e s t s t a n d " , a m e c h a n i c a l m o d e l of a n ID
w i t h w h i c h a l l o w e d us to try a n d d e b u g the control s y s t e m before h a v i n g the actual d e v i c e s . T h e test s y s t e m
h a d only t h e g a p drive a n d t h e linear e n c o d e r s for t w o
a x e s (the m a g n e t i c f o r c e s b e i n g s i m u l a t e d by c o m p e n s a t i n g s p r i n g s ) , but t u r n e d out to be a n e x t r e m e l y v a l u able d e v e l o p m e n t tool. W i t h o u t the t e s t s t a n d it w o u l d
have b e e n a l m o s t impossible to m e e t t h e c o n s t r u c t i o n
time schedule.
For t h e W 6 1 , it w a s sufficient to have s t e p p e r m o t o r s
a n d a n o p e n loop control with t h e capability to m o n i tor t h e linear e n c o d e r s a n d , if necessary, do a position
correction. T h e device has two axes with two separate m o t o r s that have to run s y n c h r o n o u s l y to k e e p the
taper, i.e., t h e inclination a n g l e of the m a g n e t arrays,
I
1
V
1
Rotary encoder US (left
Rotary encoder DS (left
Linear encoder US (right
Linear encoder DS (right
\
J
Mi
\l
i
/
1
^
scale)^" scale/ —
scale)
scale)
fi
\ ; !
\
/
F i g . 1 : Elliptical u n d u l a t o r U E 5 6 : g a p c h a n g e (i.e. p h o t o n e n e r g y ) d u r i n g a d y n a m i c a l c h a n g e of the shift
m o d e (i.e. p h o t o n polarization). O n c e t h e four drive
a x e s are o p e r a t e d in a c l o s e d loop position control using t h e linear e n c o d e r s , the m e a s u r e d d y n a m i c a l g a p
c h a n g e s stay b e l o w l ^ m over t h e full range of t h e shift
travel ( ± 2 8 m m ) .
c l o s e to zero. T h e U E 5 6 t w i n - u n d u l a t o r h a s m o r e d e m a n d i n g r e q u i r e m e n t s . T h e s e d e v i c e s have t h e p o s s i bility to c h a n g e t h e light polarization f r o m linear to elliptical by shifting u p p e r a n d lower m a g n e t a r r a y s longitudinally relative to e a c h other (shift m o d e ) . T h e large
m a g n e t i c f o r c e s (several tons) p u s h t h e g a p m e c h a n i cally o p e n w h e n the m a g n e t arrays are shifted. T h e diff e r e n c e h a d b e e n m e a s u r e d to b e a l m o s t 3 0 0 m i c r o n s
(Figure 1), w h i c h is not a c c e p t a b l e for user o p e r a t i o n .
T h e s y s t e m t h u s required c l o s e d - l o o p position c o n t r o l ,
w i t h four a x e s to control simultaneously. T h e drive s y s tem uses AC servomotors. The conventional way would
be to u s e rotary e n c o d e r s o n the m o t o r s for t h e position f e e d b a c k , but to get the required high p r e c i s i o n ,
w e d e c i d e d to do a f e e d b a c k directly f r o m the linear e n c o d e r s . T h i s is m o r e difficult to t u n e , b e c a u s e the e n tire m e c h a n i c a l s y s t e m is i n c l u d e d in t h e f e e d b a c k loop
a n d the c o m p o n e n t s c a n n o t be t u n e d individually. H o w ever, this simplifies the additional s o f t w a r e b e c a u s e the
regulation is directly b a s e d on t h e g a p r e a d i n g a n d no
f u r t h e r c o r r e c t i o n s are n e e d e d to a c c o u n t for b a c k l a s h ,
b e n d i n g a n d c r e e p . W e have a c h i e v e d l ^ m precision
a n d repeatability for t h e U E 5 6 g a p - a n d shift drive. T h e
polarization m o d e c a n be c h a n g e d d y n a m i c a l l y a n d the
70
feedback keeps the gap value (and hence the photon
e n e r g y ) to its setpoint r e g a r d l e s s of the highly nonlinear m a g n e t i c f o r c e s arising f r o m t h e m a g n e t array shift
m o t i o n to c h a n g e the p h o t o n polarization. T h i s feature
will be crucial for a s i m u l t a n e o u s s c a n n i n g of t h e u n d u lator g a p a n d t h e m o n o c h r o m a t o r energy.
In a d d i t i o n , in c a s e of the i n - v a c u u m U 2 4 undulator, it
s e r v e s a s a n indicator of possible p r o b l e m s in the w a t e r
c o o l i n g circuit. In this device, t h e control p r o g r a m c o n stantly m o n i t o r s the t e m p e r a t u r e a n d if it rises a b o v e a
s p e c i f i e d t h r e s h o l d , the g a p is a u t o m a t i c a l l y o p e n e d .
T h e t e m p e r a t u r e s are m e a s u r e d with t h e r m o c o u p l e s
a n d G r e e n s p r i n g [7] t h e r m o c o u p l e IP c a r d s .
Electromagnetic Devices
An electromagnetic UE212 twin-undulator has been
installed in the long straight s e c t i o n 9 L . T h e s e d e v i c e s have no m o v i n g g a p but i n s t e a d the c u r r e n t s
of t h e e l e c t r o m a g n e t s n e e d to be c o n t r o l l e d for vario u s m o d e s of o p e r a t i o n : linear/circular polarization a n d
p e r i o d i c / q u a s i - periodic field setting. For t h e control the
s a m e digital p o w e r s u p p l i e s are u s e d a s for all t h e S L S
m a g n e t s . T h e r e f o r e m o s t of the control s y s t e m develo p e d for the s t o r a g e ring m a g n e t s c a n be u s e d . To
control hysteresis a n d end-field c o m p e n s a t i o n effects,
all p o w e r s u p p l i e s track e a c h o t h e r d u r i n g a field ramp.
Additional systems
For t h e o p e r a t i o n of the insertion d e v i c e s , additional
m o n i t o r i n g s y s t e m s are n e c e s s a r y to g u a r a n t e e the
safety of the o p e r a t i o n a n d to o p t i m i z e t h e performance.
Beam Position Monitors
For m o n i t o r i n g the b e a m position c l o s e to t h e insertion
d e v i c e , w e u s e a s e p a r a t e b e a m position m o n i t o r s y s t e m , c o n s i s t i n g of pick-up e l e c t r o d e s , a B P M p r o c e s s ing m o d u l e (Bergoz) [5] a n d an ( S L S s t a n d a r d ) A D C to
r e c o r d t h e positions. T h e m a i n p u r p o s e of t h e s e B P M s
is to provide s i g n a l s to an external interlock s y s t e m that
w o u l d d u m p the b e a m if t h e b e a m orbit h a d a too large
position offset or s t e e r i n g a n g l e at t h e insertion device.
In a d d i t i o n , t h e s e B P M s have p r o v e n to be v e r y v a l u able to m o n i t o r t h e effect of the IDs o n t h e b e a m bec a u s e they are s i t u a t e d c l o s e to the ID, giving direct
information of the b e a m orbit at that location. Further
s t u d y is still n e e d e d to fully u n d e r s t a n d t h e r e s p o n s e
a n d calibration of this (analog) B P M s y s t e m .
Beam Loss Monitors
B e a m loss m o n i t o r s have b e e n installed near the insertion devices.
Especially critical is the small g a p
u n d u l a t o r U 2 4 ( i n - v a c u u m ) o p e r a t i n g at g a p s a s small
a s 6.5 m m , w h e r e large a r e a scintillator p a d d l e s have
b e e n installed. T h e scintillator p a d d l e s are v e r y s e n sitive to the b e a m loss rate with a fast t i m e r e s p o n s e .
T h e y p r o v e d to b e v e r y useful d u r i n g c o m m i s s i o n i n g .
T h e o u t p u t f r o m the b e a m loss m o n i t o r s are T T L signals. Its f r e q u e n c y p r o v i d e s the loss rate. T h e T T L
s i g n a l s are read out with a (SIS [8]) m u l t i c h a n n e l scaler
into E P I C S c h a n n e l s .
Correctors
E a c h ID h a s horizontal a n d vertical c o r r e c t o r m a g n e t s
p l a c e d c l o s e to the d e v i c e u p s t r e a m a n d d o w n s t r e a m .
T h e s e c o r r e c t o r s are u s e d to m i n i m i z e the effect of the
residual kicks f r o m t h e ID at different settings. T h e corrector v a l u e s for e a c h g a p setting follow b r e a k p o i n t tables that have b e e n m e a s u r e d d u r i n g c o m m i s s i o n i n g of
e a c h device.
Magnetic Field Monitoring
For control of t h e hysteresis of the U E 2 1 2 electrom a g n e t i c t w i n - u n d u l a t o r s d u r i n g small field variations,
t h e m a g n e t i c fields will be m o n i t o r e d on-line u s i n g
H a l l - p r o b e s installed in small p o r t s of t h e v a c u u m a n t e c h a m b e r c l o s e to the b e a m axis.
User Interface
A l t h o u g h t h e d e v i c e s are v e r y different, m u c h effort h a s
b e e n m a d e to m a k e t h e m look similar to t h e o p e r a t o r
a n d to hide t h e (different levels of) c o m p l e x i t y b e h i n d a
c o m m o n o p e r a t i n g interface. Basically, only a m i n i m u m
of information is p r e s e n t e d o n the o p e r a t o r display. T h e
o p e r a t o r n o r m a l l y c a n only switch t h e m o t o r drives o n
or off a n d to set t h e g a p to t h e r e q u i r e d value. Before
t u r n i n g o n the p o w e r for instance, the d e v i c e s go internally t h r o u g h a s e r i e s of c h e c k s a n d settings (the g a p
setpoint is s y n c h r o n i s e d with the actual g a p value, for
instance) before t h e m o t o r p o w e r is t u r n e d o n .
REFERENCES
[1] G. Ingold, T. S c h m i d t , Insertion Devices installed at
the SLS (Phase I), PSI Scientific R e p o r t 2 0 0 1 , V I I .
[2] W. B u l g h e r o n i , T. K o r h o n e n , C. Vollenweider, G. Ing o l d , T. S c h m i d t , Insertion
Devices:
Gap
Control
Hardware,
PSI Scientific R e p o r t 2 0 0 1 , V I I .
[3] A. L u e d e k e et.al.,Digital
Power Supplies
for the
Swiss Light Source, I C A L E P C S ' 0 1 , S a n J o s e , C a l ifornia, U S A .
[4] T. K o r h o n e n , M. Heiniger, Timing System of the
Swiss Light Source, I C A L E P C S ' 0 1 , S a n J o s e , C a l ifornia, U S A .
[5] B e r g o z SA., BPM system
user's
Manual.
[6] H e i d e n h a i n G m B H . w w w . h e i d e n h a i n . c o m
[7] S B S G r e e n s p r i n g , w w w . g r e e n s p r i n g . c o m
Temperature measurement
M o n i t o r i n g of the v a c u u m c h a m b e r t e m p e r a t u r e is a
safety m e a s u r e a g a i n s t h e a t i n g w h e n t h e orbit is b a d .
[8]
SISGmBH.www.sis.de
[9] O r e g o n M i c r o s y s t e m s , Co.. w w w . o m s m o t i o n . c o m
71
STATUS OF THE MYTHEN DETECTOR SYSTEM
B. Schmitt, Ch. Brönnimann,
E.F. Eikenberry,
M. Naef, F. Gozzo, D. Maden, B.D.
Patterson,
R. Horisberger,
J. Rothe, S. Streuli, J. Welte, C. Hörmann (University
of Erlangen)
A detector module of the MYTHEN
detector (Microstrip
System for Time resolved
experiments)
was installed at the powder diffraction
station [1,2] of the Material Science beamline [3]. The module was successfully tested and first user experiments
were performed
showing the potential of the detector
system.
Due to the large angular coverage
and the fast readout time, the microstrip
detector allows major improvements
for time-resolved
measurements.
DETECTOR SYSTEM
STATUS
T h e M Y T H E N d e t e c t o r s y s t e m c o v e r s , in parallel, an
a n g u l a r r a n g e of 6 0 ° in 26. T h e n u m b e r of c h a n n e l s is
1 5 0 0 0 . T h e pitch of the strips on the s e n s o r s is 5 0 u.m,
w h i c h c o r r e s p o n d s t o an intrinsic a n g u l a r resolution of
0 . 0 0 4 ° . T h e d i a m e t e r of t h e capillary, h o w e v e r , limits
the a n g u l a r resolution (e.g. 0.011° for a 0.1 m m c a p i l lary).
D u r i n g s u m m e r 2 0 0 1 , 13 m o d u l e s w e r e f a b r i c a t e d .
T h e m o d u l e s w o r k well, h o w e v e r , d u e t o an u n e x p e c t e d p r o b l e m with the w i r e b o n d i n g , t h e s e m o d u l e s
h a v e a rather large n u m b e r of d e a d c h a n n e l s ( 4 % 1 7 % per m o d u l e ) .
READOUT ELECTRONICS
T h e d e t e c t o r s y s t e m c o n s i s t s of 12 s u b - m o d u l e s e a c h
having 1 2 8 0 c h a n n e l s . T h e d e t e c t o r m o d u l e s are c o n n e c t e d t o a d e t e c t o r control b o a r d that routes all t h e
control signals c o m i n g f r o m a V M E pattern g e n e r a t o r
to t h e m o d u l e s . It a l s o distributes t h e s u p p l y v o l t a g e s
to t h e m o d u l e s a n d t r a n s m i t s the data c o m i n g f r o m
the m o d u l e s to a digital input c a r d . T h e input c a r d at
the m o m e n t is a V M E m o d u l e w h i c h will ultimatetly be
r e p l a c e d by a PCI c a r d installed in a P C . Fig. 1 s h o w s
six m o d u l e s a n d the d e t e c t o r control b o a r d .
T h e d e t e c t o r control b o a r d will be t e s t e d in F e b r u a r y
2 0 0 2 . In M a r c h 2 0 0 2 , the d e t e c t o r control b o a r d t o g e t h e r with 12 m o d u l e s will be installed. A d d i t i o n a l
m o d u l e s will be built to s u c c e s s i v e l y replace t h e m o d ules with n e w m o d u l e s h a v i n g less d e a d c h a n n e l s .
In A u g u s t 2 0 0 1 , the entire d e t e c t o r m e c h a n i c s a n d
o n e m o d u l e w a s installed at the b e a m l i n e . T h e m o d u l e
w a s s u c c e s s f u l l y t e s t e d a n d h a s b e e n routinely u s e d
for m e a s u r e m e n t s .
FIRST M E A S U R E M E N T S
T h e first u s e r e x p e r i m e n t ( p e r f o r m e d with I. Müller,
University M ü n s t e r ) w a s a t i m e resolved e x p e r i m e n t to
s t u d y the t i m e d e p e n d e n c e of c h e m i c a l p h a s e s during
t h e h a r d e n i n g p r o c e s s of c e m e n t . Fig. 2 s h o w s the
result.
Cement Hardening, 132 keV
-iJL
ft
A
11
X~ ~ J L
F i g . 1 : Six d e t e c t o r m o d u l e s a n d the d e t e c t o r control
b o a r d . T h e m o d u l e s will be c o n n e c t e d to t h e detector
control b o a r d t h r o u g h flat b a n d c a b l e s . T h e d e t e c t o r
control b o a r d routes t h e control signals t o the m o d u l e s
a n d t h e data t o a n input m o d u l e .
T h e r e a d o u t t i m e of t h e entire d e t e c t o r s y s t e m will be
2 4 4 u s . During readout, t h e data rate will be
150 M B y t e s per s e c o n d . T h e d a t a v o l u m e will be
3 5 k B y t e s per i m a g e . T h e n u m b e r of i m a g e s per s e c o n d is limited by t h e s t o r a g e rate of the PC to a b o u t
1 0 0 0 i m a g e s per s e c o n d .
ll, K
7
30 min
L a
-J—i^,
6
A
8
9
"*
,5mfc
m l n
10
1
2©[DEG]
F i g . 2 : T i m e d e p e n d e n c e of different p h a s e s during
the cement hardening process.
72
Data w e r e repetitively a c c u m u l a t e d for periods of
30 s e c o n d s . In that w a y t h e h a r d e n i n g p r o c e s s w a s
closely m o n i t o r e d for t h e first hour during w h i c h structural c h a n g e s h a p p e n o v e r a short t i m e s c a l e (seco n d s to m i n u t e s ) . After t h e first hour, t h e r e a c t i o n s
s l o w d o w n significantly a n d only m e a s u r e m e n t s at
s e v e r a l h o u r s t i m e interval a r e n e c e s s a r y . T h e data
w e r e c o r r e c t e d with a flat field illumination to c o r r e c t
for differential inefficiencies of t h e c h a n n e l s .
M o r e internal a n d external u s e r s u s e d t h e microstrip
d e t e c t o r for test m e a s u r e m e n t s . S e e for e x a m p l e
U. S t a u b [4].
REFERENCES
[1]
F. F a u t h , T h e P o w d e r Diffraction E n d S t a t i o n , P S I
Scientific Report 2 0 0 0 , V o l u m e V I I .
[2]
F. G o z z o , High Resolution
Tests at the SLS Powder Diffractometer,
PSI Scientific R e p o r t 2 0 0 1 ,
Volume VII.
[3]
B.D. P a t t e r s o n , The Material
Science
PSI Scientific Report 2 0 0 1 , V o l u m e V I I .
[4]
U. S t a u b , Structural
Disorder
below the MetalInsulator
Transition
in Ca2Ru04,
PSI Scientific
Report 2 0 0 1 , V o l u m e VII.
Beamline,
73
STATUS OF THE PILATUS PROJECT
Ch. Brönnimann,
E.F. Eikenberry,
R. Horisberger,
G. Hülsen,
M. Näf,
B. Schmitt,
S.
Streuli
A large step in the development
of a quantum-limited
large-area
pixel detector (PILATUS)
was
accomplished by manufacturing
the first modules, each consisting of one silicon sensor plate and 16 CMOS readout chips. The performance
of the modules is well adapted to the needs of protein crystallography:
X-rays
above 6 keV with peak count rates exceeding
500 kBq/pixel
can be detected
in single photon
counting
mode. An excellent point spread function together with a short read out time of 5 ms are other properties
of
this new type of detector. To demonstrate
the potential of this detector, data were taken at the
PX-Beamline 6S with an assembly of 3 modules.
T h e last year w a s d e d i c a t e d to the fabrication of t h e
first pixel m o d u l e s . U p o n arrival of t h e P I L A T U S
C M O S w a f e r s in M a y 2 0 0 1 a n d s u c c e s s f u l c o m p l e t i o n
of basic tests, the p r o c e s s i n g for b u m p b o n d i n g w a s
started at P S I . T h i s p r o c e s s i n g of t h e C M O S w a f e r s
involves: p h o t o l i t h o g r a p h y for U B M ( U n d e r b u m p
Metal), sputtering of U B M , i n d i u m e v a p o r a t i o n , lift off
a n d dicing of t h e w a f e r s . For the s e n s o r w a f e r s : p h o tolithography for i n d i u m e v a p o r a t i o n , i n d i u m e v a p o ration, lift off a n d dicing of the w a f e r s . T h e s e s t e p s
w e r e s u c c e s s f u l l y e s t a b l i s h e d o n 8 C M O S a n d 20
sensor wafers.
O n A u g u s t 8 t h , the first single chip m o d u l e w a s t e s t e d
a n d i m a g i n g c o u l d be p e r f o r m e d with a F e s o u r c e
(6 k e V ) . In parallel, t h e r e a d o u t - e l e c t r o n i c s a n d the
s o f t w a r e w e r e p r e p a r e d for t h e o p e r a t i o n of a 16-chip
m o d u l e . O n A u g u s t 16th, t h e first multi-chip m o d u l e
w a s m a n u f a c t u r e d a n d t e s t e d in the lab. It c o n s i s t s of
16 c h i p s containing 5 7 4 6 2 pixels.
5 5
T h e p e r f o r m a n c e of t h e m o d u l e s is r e m a r k a b l e : with
an o p t i m i s e d t h r e s h o l d t r i m m i n g a l g o r i t h m , a m i n i m u m
t h r e s h o l d of < 1 0 0 0 e" (3.6 k e V ) with a variation of 8 8 e"
c o u l d be a c h i e v e d .
fe
• I l l l i l i M B l l
V ' » * ' « * » * *¿* v**<ti*
1
«8 «
f r o m 2.3 % initially to b e l o w 0.4 %. H o w e v e r , usually
o n e of t h e 16 c h i p s w a s d a m a g e d during the b u m p b o n d i n g p r o c e s s . W e believe that this w a s c a u s e d by
Si particles r e m a i n i n g after w a f e r dicing. By i m p r o v i n g
t h e c l e a n i n g p r o c e d u r e s a n d optical i n s p e c t i o n s prior
t o the b u m p - b o n d i n g p r o c e s s , w e e x p e c t that this
p r o b l e m will be s o l v e d .
A n o t h e r crucial s t e p w a s p e r f o r m e d by g r o u p i n g
3 m o d u l e s t o g e t h e r to f o r m a b a n k (Fig. 1 ). M a n y d i a g nostic f e a t u r e s are i n c o r p o r a t e d : E a c h pixel c a n be
a d d r e s s e d for t h r e s h o l d t r i m m i n g , calibration or m o n i toring of its a n a l o g s i g n a l . R e a d o u t of the s t o r e d data
is d o n e in parallel a n d t a k e s 5 m s , after w h i c h the
detector is r e a d y to start t h e next e x p o s u r e . T h e data
are intermediately s t o r e d o n the s o - c a l l e d b a n k control
b o a r d (visible t o w a r d the b a c k in Fig. 1), f r o m w h e r e
t h e y are r e a d into a V M E F I F O m o d u l e .
T h e a s s e m b l y w a s s u c c e s s f u l l y t e s t e d at t h e protein
c r y s t a l l o g r a p h y b e a m l i n e 6 S . W i t h a K B r s o l u t i o n , flat
field calibrations w e r e p e r f o r m e d at 12 k e V .
^
i.
I
• • • 1 1 1
F i g . 1 : T h e a s s e m b l y of 3 pixel m o d u l e s t o g e t h e r with
their r e a d o u t electronics. T h e x-ray s e n s o r s are in the
immediate
foreground.
The
active
area
is
2 4 0 x 3 4 m m a n d c o n s i s t s of 1 7 2 3 8 6 pixels. It is the
largest pixel a s s e m b l y of its kind currently available.
2
T h e quality of the b u m p b o n d i n g w a s steadily i m p r o v e d . T h e n u m b e r of m i s s i n g b u m p b o n d s d r o p p e d
F i g . 2 : Diffraction pattern of a lyzozyme crystal rec o r d e d with the pixel detector at 12 k e V . T h e oscillation is 1 ° with 2 s e x p o s u r e t i m e . T h e c o m p l e t e diffraction pattern w a s o b t a i n e d by r e c o r d i n g data at
7 vertical positions.
74
A c o m p l e t e d a t a s e t f r o m a l y z o z y m e crystal w a s t a k e n
with t h e pixel detector. For that, the d e t e c t o r w a s
m o v e d in t h e vertical direction; at e a c h of 7 positions
an oscillation r a n g e of 5 0 ° w a s c o v e r e d in 1 ° s t e p s
with 2 s e x p o s u r e t i m e . T h e pixel detector w a s opera t e d u n d e r t h e control P C of the high resolution diffractometer.
S o m e p r o b l e m s r e m a i n c o n c e r n i n g the yield of t h e
r e a d o u t c h i p s . T h e c h i p s d e l i v e r e d up t o n o w h a v e on
a v e r a g e ~ 5 % d e a d pixels, d u e to d e f e c t s in both t h e
a n a l o g a n d the digital part. T h e f a c t o r y will p r o c e s s 10
m o r e w a f e r s with i m p r o v e d yield. A n overall d e f e c t
rate of a b o u t 3 % d e a d pixels (including b u m p b o n d i n g
plus d e f e c t s o n t h e s e n s o r ) c a n be e x p e c t e d for t h e
next m o d u l e s w h i c h will be built.
T h e p r o d u c t i o n p h a s e of t h e 2 0 m o d u l e s for t h e
1 0 0 0 x 1 0 0 0 d e t e c t o r will start in M a r c h , 2 0 0 2 . Until
t h e n , t h e quality of t h e b u m p - b o n d i n g will be i m p r o v e d
by the e x p e r i e n c e w h i c h is being g a i n e d by fabricating
the 10 first m o d u l e s . In o r d e r t o s p e e d up the m a n u facturing p r o c e s s , a r e d e s i g n of t h e r e a d o u t e l e c t r o n ics is being u n d e r t a k e n .
T h e T V X - s o f t w a r e s y s t e m a n d Data
flexible, running reliably a n d stably.
quisition of the data is still d o n e via
standard SLS V M E - C P U system,
placed soon.
acquisition is v e r y
However, the acthe relatively s l o w
w h i c h will be re-
A n i m p o r t a n t contribution w a s m a d e by our c o l l a b o rators, the S P r i n g 8 Detector G r o u p . H. T o y o k a w a
participated in t h e c o m i s s i o n i n g of the d e t e c t o r s during
a 2 m o n t h visit t o the S L S . W e w o u l d like t o t h a n k
F. G l a u s ( L M N ) a n d M. H o r i s b e r g e r ( L N S ) for their
p r e p a r a t i o n s for the b u m p b o n d i n g , C h . Bühler for the
m a n u f a c t u r i n g of t h e B C B a n d J . R o t h e for t h e m e chanics.
75
MILLISECOND-SHUTTER FOR EXPOSURE CONTROL
C. Pradervand,
D.
Rossetti
The precise exposure
of samples to the x-ray beam is needed
ms-shutter
was developed
to control the exposure
time.
INTRODUCTION
W i t h m o d e r n s y n c h r o t r o n s , t h e n e e d t o control t h e
e x p o s u r e t i m e of the s a m p l e s to t h e x - r a y s b e c o m e
m o r e important. A s e x p o s u r e t i m e s get shorter, t h e
c o o r d i n a t i o n b e t w e e n spindle m o v e m e n t a n d s h u t t e r
o p e n i n g n e e d s to be m o r e a c c u r a t e in o r d e r to m i n i m i z e errors a n d get r e p r o d u c i b l e e x p o s e d i m a g e s . For
t i m e r e s o l v e d x - r a y e x p e r i m e n t s , w h e r e v e r y short
e x p o s u r e s are r e q u i r e d , a fast s h u t t e r c a n isolate a
single b u n c h f r o m a b u n c h train.
SYSTEM OVERVIEW
A s i n g l e - s h o t shutter w a s d e v e l o p e d a n d built at t h e
S L S . It c o n s i s t s of a m e c h a n i c a l shutter, w h i c h c o n trols t h e e x p o s u r e a n d control e l e c t r o n i c s that drive
the s h u t t e r a n d c a n easily be interfaced t o a n y control
s y s t e m . T h i s s h u t t e r is b a s e d o n a d e s i g n u s e d in a
s h u t t e r train for t i m e r e s o l v e d e x p e r i m e n t s [1] a n d h a s
b e e n r e d e s i g n e d a n d o p t i m i z e d in t e r m s of s p e e d ,
size a n d manufacturability.
for reliable
data acquisition.
A
single-shot
blade c o r r e s p o n d s to a solid block of o v e r 9 m m thickn e s s in p e r p e n d i c u l a r g e o m e t r y . T h e blade c a n a l s o
be c o a t e d to i n c r e a s e t h e a b s o r p t i o n of higher e n e r g y
x-rays.
DRIVE ELECTRONICS
A p a r t f r o m the m e c h a n i c a l g e o m e t r y of t h e shutter,
t h e m a i n r e a s o n for t h e s p e e d is t h e s p e c i a l drive
e l e c t r o n i c s . Driving the s o l e n o i d m a g n e t s s i m p l y by
t u r n i n g t h e m o n or off w o u l d result in a rather s l o w
m o t i o n of t h e s h u t t e r d u e t o t h e s l o w m a g n e t i z a t i o n of
t h e coils. S p e c i a l drive e l e c t r o n i c s w e r e d e v e l o p e d
a n d o p t i m i z e d in o r d e r t o a c h i e v e fast s w i t c h i n g t i m e s .
A n o t h e r f u n c t i o n of t h e e l e c t r o n i c s is to allow for a
s i m p l e interface t o a control s y s t e m . T h e shutter is
controlled by a T T L signal. 0 V c l o s e s the shutter a n d
5 V o p e n s t h e shutter. Fig. 2 s h o w s t h e T T L pulse a n d
t h e resulting o p e n i n g f u n c t i o n for a 2 m s e x p o s u r e
m e a s u r e d w i t h a laser b e a m of a b o u t 1 m m size.
:
6
A:
@:
:
DESCRIPTION
:
i.96ms
1.98ms
:
:
A:
@:
:
:
280mV
1.40 V
*
.
1
j
]
T h e m s - s h u t t e r c o n s i s t s of t w o m a i n parts, the m e c h a n i c a l shutter a n d t h e drive electronics. T h e shutter
itself is a s m a l l steel blade, w h i c h c a n t o g g l e a r o u n d
a n a x i s s u p p o r t e d by t w o ball b e a r i n g s .
f -
-
:chi
s.oo v
11
:
:
-\
2.00 V
:
:
:
:
:
:
]
-
M 1.00ms A Ch1 S
: iï^^.oooooms
2.30 Vi
j
F i g . 2 : O p e n i n g f u n c t i o n of the shutter
F i g . 1 : m s - s h u t t e r in a n o p e n v i e w
T h e blade is driven by t w o s o l e n o i d m a g n e t s a n d h a s
a travel of 2 m m . T h e a d v a n t a g e of this d e s i g n o v e r
o n e with only o n e s o l e n o i d m a g n e t a n d a s p r i n g retraction is a s y m m e t r i c a l o p e n i n g f u n c t i o n a n d higher
speed. The geometry was optimised to operate the
s h u t t e r near the f o c a l s p o t of the b e a m , for b e a m
s i z e s b e l o w 1 m m vertically a n d 4 m m horizontally. In
the c l o s e d position the blade is at a s h a l l o w a n g l e . At
this a n g l e , with a vertical size b e a m of 5 0 0 urn, the
M i n i m a l o p e n t i m e s of a b o u t 8 0 0 u s h a v e b e e n
a c h i e v e d . A l t h o u g h t h e o p e n t i m e is s o m e w h a t b e a m
size d e p e n d e n t , t h e o p e n i n g f u n c t i o n f o l l o w s the T T L
pulse v e r y w e l l , with a f i x e d ( g e o m e t r y - d e p e n d e n t )
d e l a y of a b o u t 2 m s . T h e rise t i m e a n d fall t i m e of the
o p e n i n g resp. closing e d g e are a b o u t 3 0 0 u s . T h e y
are c o n s t a n t , g i v e n by the g e o m e t r y a n d drive elect r o n i c s a n d are not d e p e n d e n t o n the o p e n t i m e .
REFERENCES
[1]
D. B o u r g e o i s et al., Feasibility
and Realization
of
Single-Pulse
Laue Diffraction
on
Macromolecular
Crystals
at ESRF, J . S y n c h r o t r o n R a d . 3, 6 5
(1996).
76
THE BEAMLINES DATA ACQUISITION AND CONTROL SYSTEM
J. Krempasky,
D. Vermeulen,
D. Maden, M. Janousch,
R.
Krempaská,
T. Korhonen,
W. Portmann,
M. Grunder, S. Hunt
The commissioning
of the first four beamlines
(Protein
Crystallography,
Material
Science,
Surfaces/Interfaces
Spectroscopy
and Surfaces/Interfaces
Microscopy)
at SLS started in April 2001 and by
the end of November 2001 all of them delivered beam to their experimental
environments.
This very tight
time schedule clearly indicates that the EPICS control system toolkit provided valuable help in the
beamline
commissioning.
An important aspect of the SLS beamlines is the fact that they benefit from the same
EPICS
based control system as the SLS machine.
This involves both hardware and software and allows
smooth
integration
of several sub-systems
(monochromator,
insertion device, beam diagnostics
etc).
"The Experiment"
Usage of s y n A p p s package o n the SLS Beamlines
T h e bulk of c u s t o m b e a m l i n e control software is
t a k e n f r o m s y n A p p s p a c k a g e [2].
It i n c l u d e s softw a r e s u p p o r t for m o t o r s , s c a l e r s , optical tables, slits,
multidimensional scans, multichannel analyzers and
m i s c e l l a n e o u s d e v i c e s . T h e s u p p o r t for m o t o r s (both
s t e p p i n g a n d s e r v o m o t o r s ) p r o v i d e d by the E P I C S
m o t o r r e c o r d , fits well with the O r e g o n Micro S y s t e m s
V M E 5 8 family of intelligent m o t i o n controls, g e n e r a l l y
u s e d for m o t i o n control o n all b e a m l i n e s . A m o n o c h r o m a t o r c a n b e c o n s i d e r e d as a collection of s u c h
m o t o r s . T h e y c a n b e driven a c c o r d i n g to s p e c i a l t a b l e s
or analytic e x p r e s s i o n s d e f i n e d by E P I C S cale r e c o r d s .
EPICS Hardware (VME Crates)
F i g . 1 : S c h e m a t i c a l layout of a b e a m l i n e e x p e r i m e n t .
T h e functionality of the s u b - s y s t e m s resides in V M E
c r a t e s s e e n o n t h e lower part of t h e figure. O n t h e
u p p e r part t h e r e are b e a m l i n e clients d o i n g the e x p e r i m e n t s i m p l e m e n t e d as s i m p l e scripts.
INTRODUCTION
T h e c o n t r o l s a n d d a t a acquisition s y s t e m of t h e S L S
b e a m l i n e s is closely integrated with t h e m a c h i n e c o n trol s y s t e m . It is b a s e d o n E P I C S , a client-server toolkit
with C A ( C h a n n e l A c c e s s ) s e r v e r s r u n n i n g o n V M E proc e s s o r s ( P o w e r P C ) , a n d clients r u n n i n g Linux ( R e d H a t
6.2) or N T P C s [1]. T h e position a n d functionality of
t h e V M E c r a t e s follow the b e a m l i n e t o p o l o g y (typically
f r o n t - e n d , m o n o c h o m a t o r , b e a m l i n e optics, e x p e r i m e n tal station 1 , 2...) a n d clearly d e t e r m i n e a b e a m l i n e
s u b - s y s t e m (see Fig. 1). T h e total n u m b e r of V M E
c r a t e s per b e a m l i n e is 4-5. S o m e s u b - s y s t e m s have
b e e n (will be) d e l i v e r e d a l r e a d y with E P I C S drivers,
for e x a m p l e t h e J e n o p t i k Plane G r a t i n g M o n o c h r o m a t o r
and C O P H E E ( C o m p l e t e PHotoEmission Experiment)
e x p e r i m e n t a l station. T h e i r inclusion into t h e b e a m l i n e
E P I C S e n v i r o n m e n t is straightforward, w h i c h greatly facilitates a n d s p e e d s u p the b e a m l i n e c o m m i s s i o n i n g .
A n o t h e r v e r y useful s u p p o r t f r o m s y n A p p s is t h e so
c a l l e d sscan E P I C S r e c o r d . It allows for a d y n a m i c c o n figuration of v a r i o u s t y p e s of s c a n s b a s e d on E P I C S
p r o c e s s variables. T h i s feature is of particular interest
for b e a m l i n e c o m m i s s i o n i n g w h e r e o n e c a n p e r f o r m a
r u n - t i m e c o n f i g u r a t i o n of 1 D / 2 D s c a n s with several p o sitioners, d e t e c t o r s a n d d e t e c t o r triggers. T h e s c a n
results c a n b e a u t o m a t i c a l l y s a v e d f r o m t h e V M E Inp u t / O u t p u t C o n t r o l l e r ( I O C ) to a file s e r v e r - a n o t h e r
v e r y useful feature c a l l e d saveData f r o m the s y n A p p s
p a c k a g e (there is o n e d e d i c a t e d file s e r v e r for e a c h
beamline).
S i m p l y put, o n e c a n p e r f o r m s i m p l e or
s o p h i s t i c a t e d s c a n s w i t h o u t involving c o d i n g o n s o m e
clients.
Usage of SDDS o n the SLS Beamlines
T h e Material S c i e n c e B e a m l i n e at the S L S is currently
m a k i n g extensive u s e of the S D D S (Self D e s c r i b i n g
D a t a Set) [3] utilities a n d E P I C S c l i e n t - b a s e d a p p l i c a tions d e v e l o p e d at t h e A P S for b e a m l i n e t u n i n g a n d
d a t a acquisition s c a n s of t h e p o w d e r diffractometer. In
particular, the G U I interfaces to t h e S D D S software,
s u c h a s q u i c k E x p e r i m e n t [4], have f o u n d a c c e p t a n c e
by t h e b e a m l i n e scientists d u r i n g t h e early s t a g e s of
b e a m c o m m i s s i o n i n g . At a later date, it is i n t e n d e d that
m o r e s c i e n c e - o r i e n t e d s o f t w a r e will b e i n t r o d u c e d . T h i s
will also m o s t likely b e c o u p l e d with a m o v e to N e X u s
[5], w h i c h is strongly s u p p o r t e d by t h e n e u t r o n scattering c o m m u n i t y at P S I .
77
IMPLEMENTING NON-EPICS HARDWARE
CCD Camera
D e s p i t e t h e fact that t h e e x p e r i m e n t a l stations m a y
b e b a s e d o n a n o n - E P I C S h a r d w a r e a n d software,
t h e r e are several possible w a y s h o w to include t h e m
into a n E P I C S s y s t e m . In this c o n t e x t w e will briefly
d e s c r i b e a C C D c a m e r a distributed architecture, a n d
t h e E P I C S i m p l e m e n t a t i o n of the S c i e n t a - G a m m a d a t a
e l e c t r o n a n a l y s e r for t h e Surfaces/Interfaces S p e c troscopy beamline.
CCD camera distributed architecture
A n e x p e r i m e n t or d i a g n o s t i c s b a s e d o n a C C D c a m e r a d a t a acquisition a n d control c o n s i s t s typically of
h e t e r o g e n o u s h a r d w a r e a n d software.
In c o l l a b o r a tion with E L E T T R A , an o p e n s y s t e m h a s b e e n develo p e d , w h e r e different s o f t w a r e c o m p o n e n t s related to
C C D d a t a acquisition a n d e v a l u a t i o n , are integrated
into a single G U I by m e a n s of C O R B A . A C C D c a m e r a C O R B A s e r v e r i m p l e m e n t s all functionalities of the
C C D c a m e r a a n d is r u n n i n g on a W i n d o w s N T operating s y s t e m . T h e client p r o v i d e s a s i m p l e a n d intuitive
graphical user interface giving a user t h e possibility to
control t h e C C D c a m e r a by initializing, setting or getting
C C D p a r a m e t e r s , or displaying an i m a g e . T h e user interface p r o v i d e s also a utility for s i m p l e i m a g e p r o c e s s ing s u c h as a d j u s t i n g c o n t r a s t a n d b r i g h t n e s s , creating a h i s t o g r a m of an i m a g e or p e r f o r m i n g arithmetic
o p e r a t i o n s o n i m a g e s . Typically an e x p e r i m e n t b a s e d
o n C C D is a s e q u e n c e of s i m p l e o p e r a t i o n s for t h e i m p l e m e n t a t i o n of w h i c h a scripting l a n g u a g e is w e l c o m e .
T h e bulk of o p e r a t i o n s o n C C D c a m e r a a n d E P I C S c o n trol s y s t e m is i m p l e m e n t e d in a J a v a c l a s s c a l l e d " O p e r a t i o n s " (see Fig. 2). By interpreting the script a p h y s i cist c a n m a k e a n i m a g e - b a s e d e x p e r i m e n t w i t h s i m p l e
script p r o g r a m s .
Controlling the Scienta electron analyser
T h e heart of t h e e x p e r i m e n t a l a p p a r a t u s for t h e Surfaces/Interfaces S p e c t r o s c o p y b e a m l i n e is a S c i e n t a G a m m a d a t a e l e c t r o n analyser. T h e control p h i l o s o p h y
for this a n a l y s e r (as s u p p l i e d by the c o m p a n y ) , is a
rather m o n o l y t h i c a p p l i c a t i o n . O n o n e side it allows for
s u p p l y i n g additional functionality, but on the other s i d e
it did not fit into a client-server m o d e l . T h i s w a s a s e rious o b s t a c l e not only for i m p l e m e n t i n g e x p e r i m e n t s ,
w h e r e t h e a n a l y s e r is c o n s i d e r e d to b e j u s t o n e part of
t h e w h o l e e x p e r i m e n t a l setup. T h e u s e of t h e E P I C S
Portable C h a n n e l A c c e s s ( A c t i v e X C A ) [6] for invoking
the analyser operation-specific functions from the Scie n t a native c o d e t u r n e d out to b e t h e m o s t s i m p l e s o lution. T h e additional c o d i n g required just the initialization of t h e E P I C S p r o c e s s variables a n d i m p l e m e n t i n g
their event h a n d l e r s . In this w a y w e p l a n t e d E P I C S proc e s s variables into t h e S c i e n t a a p p l i c a t i o n , w h i c h a l lows us n o w to s e e t h e S c i e n t a a n a l y s e r as a virtual
E P I C S IOC.
setCCDParameterO
getlmageO
displaylmage()
savelmageQ
F i g . 2: S c h e m a t i c a l layout of a distributed architecture
for controlling C C D c a m e r a including d a t a acquisition
(upper part) a n d h a n d l i n g (lower p a r t ) .
DATA S T O R A G E A N D H A N D L I N G
In v i e w of t h e different a m o u n t s a n d rates of d a t a a
flexible s c h e m e for the a c q u i s i t i o n , s t o r a g e a s well as
h a n d l i n g of t h e d a t a h a s b e e n d e v e l o p e d . T h e different
b e a m l i n e s p r o d u c e d a t a at rates r a n g i n g f r o m several
M b y t e s / h o u r to 8 0 M b y t e s / s e c . T h e total a m o u n t of acc u m u l a t e d d a t a r a n g e s f r o m G b y t e s to several h u n d r e d
G b y t e s per d a y / e x p e r i m e n t . E a c h b e a m l i n e h a s a d e d i c a t e d file s e r v e r of u p to 3 0 0 G b y t e of available s t o r a g e ,
w h i c h c a n b e easily e x t e n d e d to m o r e t h a n 1 T b y t e .
S i n c e t h e b e a m l i n e is c o n t r o l l e d f r o m a private network,
t h e file s e r v e r is e q u i p p e d with t w o n e t w o r k c a r d s that
are c o n n e c t e d to t h e private S L S - n e t w o r k a n d t h e PSI
n e t w o r k respectively (see Fig. 3). All d a t a that h a s to
leave t h e S L S h a s to go t h r o u g h this file server.
Currently, a tape-library is b e i n g set-up as a central
m e d i u m - t e r m s t o r a g e facility. It h a s a s t o r a g e c a p a c ity of 3 0 T b y t e s . U s e r s c a n , u p o n request, transfer their
d a t a to this m e d i u m . Also, they have t h e possibility to
m a k e c o p i e s of their d a t a to o t h e r m a s s - s t o r a g e m e d i a
like DLT or DAT. For the large v o l u m e d a t a (more t h a n
100 Gbyte) a n d c o m m e r c i a l users, N e t w o r k A t t a c h e d
S t o r a g e ( N A S ) or h o t - s w a p p a b l e d i s k s c a n be h o o k e d
u p to t h e d a t a - a c q u i s i t i o n c o m p u t e r s .
U s e r a c c e s s to t h e c o m p u t e r s o n the private S L S - n e t is
g r a n t e d t h r o u g h individual g r o u p a c c o u n t s , w h i c h are
c o n n e c t e d to individual a c c o u n t s on the P S I - d o m a i n
t h r o u g h t h e g r o u p - i d . T h e u s e r s at t h e b e a m l i n e c a n
d e c i d e o n t h e level of security for their data.
PSI-Net 100 Mbit
DAT
DLT
DVD
Tape
Library
j PSI-Net 1 Gbit
FTP Server
F i g . 3: S c h e m a t i c a l layout of b e a m l i n e d a t a s t o r a g e
and handling.
CONCLUSIONS
T h e c h o i c e of t h e E P I C S control s y s t e m toolkit o n t h e
S L S b e a m l i n e s clearly helps us to m e e t t h e tight t i m e
s c h e d u l e of their c o m m i s s i o n i n g . T h e g e n e r i c s o l u tions p r o v i d e d by E P I C S in principle help us to avoid
any c o d i n g . T h u s t h e software m a i n t e n a n c e a c r o s s t h e
b e a m l i n e s is m i n i m a l . A n o t h e r v e r y i m p o r t a n t a s p e c t is
t h e fact that e v e n b e a m l i n e o p e r a t o r s with no or m i n imal k n o w l e d g e a b o u t E P I C S c a n actively participate
in their c o m m i s s i o n i n g . T h e g o a l of t h e b e a m l i n e c o n trols g r o u p is to k e e p this p h i l o s o p h y valid also for the
e x p e r i m e n t a l stations. T h e u s e of t h e C O R B A archit e c t u r e t u r n s o u t to b e a g o o d a p p r o a c h for i m p l e m e n t ing e x p e r i m e n t s b a s e d o n several h e t e r o g e n e o u s s u b s y s t e m s . T h e s a m e a p p l i e s for t h e Portable C h a n n e l
A c c e s s ( A c t i v e X C A ) . It allows for s e e i n g the s p e c i a l ins t r u m e n t a t i o n functionalities living as E P I C S p r o c e s s
variables. In either c a s e , it is possible to i m p l e m e n t
v a r i o u s e x p e r i m e n t s u s i n g s i m p l e scripts w h i c h acc e s s i n s t r u m e n t a t i o n - s p e c i f i c functionalities distributed
o n t h e c o m p u t e r n e t w o r k . T h e w i d e variety of A P I s
(tcl/Tk, IDL, O c t a v e , perl...) for E P I C S a n d C O R B A is
a n o t h e r benefit for this s o l u t i o n .
REFERENCES
[1] S. H u n t et al., Status of the SLS
PSI Scientific R e p o r t 1 9 9 9 , V I I .
Control
System,
[2]
http://www.apl.anl.gov/xfd/bcda/documentation.html
[3]
http://www.aps.anl.gov/asd/oag/manuals/
[4]
http://www.aps.anl.gov/asd/newsletter/newltr22.html
[5] T h e N e X u s ( N e u t r o n & X-ray D a t a F o r m a t ) H o m e
Page: http://lnsOO.psi.ch/NeXus
[6]
http://mesa53.lanl.gov/lansce8/Epics/PC/
ActiveXCAServer/Default.htm
79
FIRST RESULTS FROM THE X-RAY TOMOGRAPHIC MICROSCOPY STATION
M. Stampanoni
(PSI, ETHZ), G. Borchert (PSI, IKP Jülich),
R. Abela, B.D. Patterson,
S. Hunt, D.
Vermeulen,
P. Wyss (EMPA),
P. Rüegsegger
(ETHZ)
The X-Ray Tomographic
Microscopy
(XTM) device has been installed successfully
at the Material
Science
Beamline
MS of the Swiss Light Source (SLS). First radiographic
projections
as well as
tomographic
scans using both absorption
and phase contrast have been acquired showing spatial resolution
down to
the micrometer
range. The instrumentation
will be used for structure and chemical analysis of new materials and biological
samples.
INTRODUCTION
X - r a y c o m p u t e r t o m o g r a p h y is a p o w e r f u l t e c h n i q u e ,
w h i c h p r o v i d e s v o l u m e t r i c d a t a of s a m p l e s by m a p ping their t h r e e d i m e n s i o n a l X - r a y a t t e n u a t i o n . It c a n
be u s e d to s t u d y p h y s i c a l a n d c h e m i c a l characteristics
of the s a m p l e s in 3 D . Originally d e v e l o p e d for clinical
u s e in radiology, X - r a y c o m p u t e r t o m o g r a p h y h a s n o w
r e a c h e d u n e x p e c t e d b r o a d a p p l i c a t i o n fields t h a n k s t o
s y n c h r o t r o n radiation. T h e high flux of s y n c h r o t r o n
radiation e n a b l e s h i g h - r e s o l u t i o n t r a n s m i s s i o n e x a m i nations in t h e m i c r o m e t e r r a n g e w i t h a r e a s o n a b l e
e x p o s u r e t i m e . E n e r g y tunability of the s y n c h r o t r o n
beam makes element-specific measurements possible. T h e high d e g r e e of c o h e r e n c e e x t e n d s t h e c l a s s i cal a b s o r p t i o n t o m o g r a p h y c o n c e p t s t o e d g e - e n h a n c e d a n d p h a s e - s e n s i t i v e investigations. T h e d e sign g o a l s of t h e S L S - i n s t r u m e n t w e r e f o c u s e d o n
t h r e e o b j e c t i v e s : high precision s a m p l e h a n d l i n g t o
a l l o w m e c h a n i c a l tests in real-time, high efficient
p h o t o n d e t e c t i o n with fast, l o w - n o i s e r e a d o u t t o a l l o w
rapid m e a s u r e m e n t s , a n d spatial resolution in the
r a n g e of 5 m i c r o m e t e r s t o 5 0 0 n m .
THE SOURCE
T h e m i n i g a p w i g g l e r s o u r c e of the Material S c i e n c e
( M S ) b e a m l i n e will radiate a total of 8.40 k W a n d prod u c e a c o n t i n u o u s s p e c t r u m of p h o t o n s with a critical
e n e r g y of 7.9 k e V . T h e a n g u l a r a c c e p t a n c e in m o n o c h r o m a t i c m o d e (5 - 4 0 k e V ) , d e t e r m i n e d by a f i x e d
c o l l i m a t o r in t h e f r o n t - e n d , is 0.23 m r a d vertical by
2.5 m r a d horizontal. A p o l y c h r o m a t i c "pink b e a m "
m o d e , up to 3 2 k e V , will be a l s o a v a i l a b l e . Vertical
c o l l i m a t i o n a n d f o c u s i n g is p r o v i d e d by v a r i a b l e a n g l e ,
v a r i a b l e - c u r v a t u r e cylindrical mirrors, w h i c h a l s o s e r v e
to e l i m i n a t e h i g h e r o r d e r h a r m o n i c s . M o n o c h r o m a t i z a t i o n is p e r f o r m e d by a fixed-exit d o u b l e crystal
m o n o c h r o m a t o r s i t u a t e d b e t w e e n t h e t w o mirrors. T h e
s e c o n d m o n o c h r o m a t o r crystal will be b e n t to p r o v i d e
horizontal f o c u s s i n g . T h e mirrors c o n s i s t of 1 m long
Si b l a n k s w h i c h are R h - c o a t e d . T h e y c a n be tilted up
to 5 m r a d a n d bent ( 5 < R < 3 0 k m ) , as required for the
desired photon energy. T h e double-crystal m o n o c h r o m a t o r c o n s i s t s of t w o S i ( 1 1 1 ) crystals w h i c h c a n
be precisely p o s i t i o n e d a n d o r i e n t e d in t h e X - r a y
b e a m . T w o s u c c e s s i v e B r a g g reflections deliver p h o t o n s with a n i n h e r e n t e n e r g y resolution of 0.014 %.
T h e optical s y s t e m will p r o d u c e a m o n o c h r o m a t i c
spectral flux d e n s i t y at 10 k e V of a p p r o x i m a t e l y 1 0
1 3
p h o t o n s / s / 0 . 1 % b w w h i c h will be f o c u s s e d into a s p o t
at the e x p e r i m e n t a l stations of m i n i m u m size of
1 m m . T h a n k s t o the t o p - u p injection m o d e , t h e intensity will be kept c o n s t a n t to a level of 10" t o 1 0 ^ ,
a n d the a p p l i c a t i o n of the m o s t recent ring c o n s t r u c tion t e c h n o l o g i e s s h o u l d p r o v i d e a v e r y stable b e a m
[1,2]. T h e s o u r c e - t o - s a m p l e d i s t a n c e for X T M is
3 5 m e t e r s , giving raise t o a d e g r e e of c o h e r e n c e
c o m p a r a b l e t o o t h e r s y n c h r o t r o n radiation s o u r c e s [3].
For this r e a s o n p h a s e - c o n t r a s t i m a g i n g , e d g e - e n h a n c e m e n t t o m o g r a p h y a n d h o l o t o m o g r a p h y c a n be
c a r r i e d o u t in addition to the classical a b s o r p t i o n
tomography.
2
3
XTM DEVICE
In a first step, w e installed a n i n s t r u m e n t b a s e d o n a
s t a n d a r d d e t e c t o r m e t h o d for routine i n v e s t i g a t i o n s of
a w i d e s p e c t r u m of s a m p l e s . T h i s i n s t r u m e n t is int e n d e d for large o b j e c t s a n d r e s o l u t i o n s of the o r d e r of
2-5 urn. In a s e c o n d step, a fully n o v e l d e t e c t o r s y s t e m (the s o called B r a g g m a g n i f i e r ) will be installed
a n d will provide a j u m p in t e r m s of spatial resolution
a n d q u a n t u m efficiency. T h e s t a n d a r d d e t e c t o r c o m b i n e s a t r a n s p a r e n t l u m i n e s c e n t s c r e e n (scintillator)
with a diffraction-limited m i c r o s c o p e optics, w h i c h
magnifies the X-ray image onto a high-performance
C C D of Pixel V i s i o n , Inc. Different C e - d o p e d Y A I 0
( Y A G ) single crystal scintillator s c r e e n s with thickn e s s e s b e t w e e n 1.8 a n d 5 0 urn, d e p o s i t e d o n a
190 urn inactive Y A G are available for v a r i o u s effic i e n c y n e e d s a n d spatial r e s o l u t i o n s r e q u i r e m e n t s .
T h e m i c r o s c o p e optics m a n u f a c t u r e d by O p t i q u e P e ter a l l o w s for a quick c h a n g e b e t w e e n different field of
v i e w s a n d v a l u e s of spatial resolution. T h e d e t e c t o r is
e q u i p p e d with a revolver, w h i c h c a n a c c o m m o d a t e
t h r e e different high-quality diffraction-limited
and
a b e r r a t i o n - c o r r e c t e d o b j e c t i v e s . T h e m i c r o s c o p e itself
c a n be a d j u s t e d in o r d e r t o e l i m i n a t e roll errors. T h e
f o c u s i n g m e c h a n i s m is controlled by a 5 0 0 - s t e p P h y tron m o t o r (driven in halfstep m o d e ) that a l l o w s for
m a t c h i n g the d e p t h of f o c u s of a b r o a d variety of o b j e c t i v e s . T h e C C D c a m e r a is e q u i p p e d w i t h a T h o m s o n T h 7 8 9 9 M full f r a m e c h i p , w h i c h
provides
2 0 4 8 x 2 0 4 8 pixels of 14 u.m pitch a n d multiple o u t p u t s .
T h a n k s t o fiber-optic c o n n e c t i o n s b e t w e e n t h e c a m e r a
a n d t h e controlling c o m p u t e r , t h e chip is r e a d - o u t
through four outputs simultaneously and independently at a s p e e d that v a r i e s f r o m 2.5 to 10 M p i x e l per
3
5
1 2
80
s e c o n d . T h i s a l l o w s for a f u l l - f r a m e r e a d o u t w i t h i n
2 5 0 m s . T h e c a m e r a h a s a n optical shutter for reducing a f t e r g l o w a n d g h o s t effect. T h e entire d e t e c t i o n
s y s t e m h a s a theoretical pixel size of 0.35 urn ( w h e n
the 2 0 x objective c o m b i n e d with the 2x o c u l a r is u s e d )
with a field of v i e w of 0.7 m m . If t h e 2x objective is
u s e d , a field of v i e w of 7 x 7 m m is g u a r a n t e e d . T h e
d e t e c t o r unit is m o u n t e d o n a 3-axis s y s t e m of
S c h n e e b e r g e r : this a l l o w s for a l i g n m e n t of the detector with r e s p e c t t o t h e b e a m a s well as the t r a n s l a t i o n
of the w h o l e unit a l o n g t h e b e a m direction. T h e s t r o k e
of this t r a n s l a t i o n is 1 1 2 4 m m a l l o w i n g for the s a m p l e d e t e c t o r d i s t a n c e t o be i n c r e a s e d up to 1 m , m a k i n g
edge-enhanced imaging and holotomography possible. T h e X T M d e v i c e installed at t h e M S B e a m l i n e is
d e p i c t e d in Fig. 1 .
o Objective 2x
O Objective 4x
a Objective 10x • Objective 20x
2
100
200
300
400
500
600
Spatial resolution [Ip/mm]
O
F i g . 2 : M T F r e s p o n s e of t h e d e t e c t o r for a Y A G : C e
scintillator with d o p e d s c r e e n of 1.8 urn t h i c k n e s s for
different o b j e c t i v e s .
11.8 microns a 20 microns o 51 microns
o
F i g . 1 : X T M Device at t h e M S B e a m l i n e : clearly visible f r o m left to right are t h e d e t e c t o r unit (1), t h e s a m ple h o l d e r (2) a n d t h e shutter/slits a s s e m b l y (3). B e a m
c o m e s f r o m t h e right.
FIRST RESULTS
T h e Modulation Transfer Function (MTF) quantitatively d e s c r i b e s the p e r f o r m a n c e of the detector in
t e r m s of spatial r e s o l u t i o n . T h e M T F of t h e s y s t e m
h a s b e e n o b t a i n e d by t h e o v e r s a m p l i n g of a 100 urn
thick t a n t a l u m e d g e . S o m e results are g i v e n in Fig. 2
a n d 3.
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
1
fc—
A—
A
O
<
0
»
100
A
1
3ü*5a5
200
300
400
500
600
Spatial Resolution [Ip/mm]
F i g . 3: M T F r e s p o n s e for the 2 0 x objective for different t h i c k n e s s e s of the C e - d o p e d Y A G s c r e e n .
Fig. 2 a n d 3 s h o w spatial resolution d o w n t o 1 m i c r o m e t e r for a 1 0 % M T F r e s p o n s e .
Exploiting the c o h e r e n t p r o p e r t i e s of t h e s y n c h r o t r o n
radiation, w e w e r e a b l e t o a c q u i r e s o m e e d g e - e n h a n c e d r a d i o g r a p h i c projections. Fig. 4 s h o w s o n e of
them.
81
lililí
F i g . 4 : E d g e - e n h a n c e d r a d i o g r a p h i c projection of a
fly's h e a d t a k e n at 9 k e V . T h e d i s t a n c e b e t w e e n s a m ple a n d d e t e c t o r w a s 100 m m .
First hints of p u r e c o h e r e n t i m a g i n g a r e illustrated in
Fig. 5, w h i c h d e p i c t s a 100 \im thick b o r o n fibre with a
15 [im t u n g s t e n c o r e a c q u i r e d at 1 5 k e V . F r a m e (A)
s h o w s t h e fibre's projection w h e n t h e s a m p l e - d e t e c t o r
d i s t a n c e is 5 0 m m . In t h e s e c o n d i t i o n s , only t h e parts
of t h e s a m p l e a r e clearly h i g h l i g h t e d ( e d g e - e n h a n c e d )
that s h o w a big c h a n g e in t h e refractive index F r a m e
(B) s h o w s t h e s a m e fibre w h e n t h e d i s t a n c e is inc r e a s e d up to 6 0 0 m m . Interference f r i n g e s d u e t o t h e
c o h e r e n t o v e r l a p p i n g of X - r a y w a v e s a r e clearly visible.
(A)
F i g . 6: R e c o n s t r u c t e d slice ( 2 0 4 8 x 2 0 4 8 ) of a n ext r e m e l y o s t e o p o r o t i c b o n e at 12 k e V . T y p i c a l artefacts
d u e t o t h e insufficient n u m b e r of projection a r e clearly
visible.
DISCUSSION and O U T L O O K
T h e X T M d e v i c e h a s b e e n s u c c e s s f u l l y installed at t h e
Material S c i e n c e B e a m l i n e . T h e m e a s u r e d p e r f o r m a n c e of t h e s t a n d a r d d e t e c t o r a g r e e s with t h e t h e o retical c a l c u l a t e d v a l u e s . Spatial resolution b e t w e e n 1
a n d 5 UJTI a r e easily r e a c h e d with a field of v i e w r a n g ing f r o m 7 m m t o 0.7 m m . First r a d i o g r a p h i c projections b o t h in a b s o r p t i o n a n d p h a s e - c o n t r a s t m o d e
h a v e b e e n o b t a i n e d . A first r o u g h t o m o g r a m h a s b e e n
a c q u i r e d s h o w i n g t h e feasibility of t h e project.
In t h e near f u t u r e , additional effort will b e i n v e s t e d in
t h e c o m m i s s i o n i n g of t h e s a m p l e h o l d e r ( E M P A ) a n d
in t h e d e v e l o p m e n t of a user-friendly interface for t h e
X T M s t a t i o n . W e e x p e c t to b e 100 % u s e r - o p e r a t i v e in
July 2 0 0 2 .
REFERENCES
[1]
B.D. P a t t e r s o n et al.,
The
Materials
Beamline,
PSI Scientific R e p o r t 1 9 9 9 ,
VII, p. 6 4 .
[2]
M. S t a m p a n o n i et al., Computer
Microtomography, PSI Scientific R e p o r t 2 0 0 0 , V o l u m e V I I ,
p. 8 1 .
[3]
T. W e i t k a m p et al., An imaging
and
graphy facility at the ESRF beamline
99, Vol. 3772.
(B)
F i g . 5: (A) E d g e - e n h a n c e d r a d i o g r a p h i c projection of
t h e b o r o n fibre a c q u i r e d at a s a m p l e - d e t e c t o r d i s t a n c e
of 5 0 m m . (B) S a m e fibre at 6 0 0 m m d i s t a n c e .
At t h e t i m e of writing this contribution t h e definitive
s a m p l e h o l d e r is e n t e r i n g t h e final c o n s t r u c t i o n p h a s e
a n d will b e t r a n s f e r r e d t o t h e S L S in late J a n u a r y
2 0 0 2 . N e v e r t h e l e s s , a primitive s i n o g r a m of a n ext r e m e l y o s t e o p o r o t i c b o n e c o u l d b e a c q u i r e d (500
projections only, no pitch a n d roll c o r r e c t i o n ) delivering t h e first r e c o n s t r u c t e d t o m o g r a p h i c slice of t h e
S L S , d e p i c t e d in Fig. 6.
Science
Volume
microtomoID22, S P I E
82
BRAGG-MAGNIFIER: HIGH PERFORMANCE X-RAY DETECTOR FOR XTM
M. Stampanoni
(PSI, ETHZ),
G. Borchert
(PSI, IKP Jülich),
R. Abela (PSI),
P. Rüegsegger
(ETHZ)
In X-Ray Tomographic
Microscopy
(XTM) experiments,
the resolution
of the standard detector
method
based on a scintillating
screen and microscope
optics is restricted by scintillator
properties,
optical light
transfer, and CCD granularity.
These factors impose a practical limit of about one micrometer,
while the
progressing
research demands
urgently an advance in the submicron
region. A break-through
in this respect is being achieved by a novel detector type. It uses the properties
of asymmetric
Bragg reflection
to
increase the cross section of the reflected X-ray beam. A suitable combination
of correspondingly
cut
Bragg crystals yields an image magnification
that even at higher energies may surpass a factor of 1000.
Simulations
as well as first experimental
characterizations
of the magnifying
unit are
presented.
INTRODUCTION
SIMULATIONS
In o r d e r t o efficiently s u r p a s s t h e m i c r o m e t e r barrier in
t e r m s of spatial resolution, a n o v e l d e t e c t i o n s y s t e m is
b e i n g d e v e l o p e d . T h e a p p r o a c h for a c h i e v i n g s u b m i c r o m e t e r resolution is t o m a g n i f y t h e i m a g e with X - r a y
optics a n d t o d e t e c t it with a l o w - r e s o l u t i o n , high-effic i e n c y detector, t h u s i m p r o v i n g both resolution a n d
efficiency. T h e optics m u s t h a v e s u b m i c r o n r e s o l u t i o n ,
efficiency a n d i m a g e fidelity. B r a g g diffraction f r o m a n
a s y m m e t r i c a l l y cut crystal p r o d u c e s o n e - d i m e n s i o n a l
m a g n i f i c a t i o n (Fig. A ) . A s e c o n d diffraction f r o m a n other crystal with t h e s a m e m a g n i f i c a t i o n factor but
p e r p e n d i c u l a r diffraction plane p r o d u c e s u n i f o r m t w o d i m e n s i o n a l m a g n i f i c a t i o n (Fig. 1B) [1].
T o build t h e B r a g g m a g n i f i e r at t h e S L S , s e v e r a l
B r a g g crystals f r o m Si a n d G e h a v e b e e n s t u d i e d . For
practical r e a s o n s , Si ( 2 2 0 ) crystals w e r e s e l e c t e d for
both crystals of t h e s e t u p . T h e r o c k i n g c u r v e s for the
i n c o m i n g a n d reflected b e a m are s h o w n in Fig. 2 [2].
s i n ( # +<x)
s
sin(#„ -a)
30
Fig. 2: Theoretical
23.1 k e V .
(A)
out
C1
(B)
curve
of
Si(220)
F i g . 1 : (A) T h e c r o s s s e c t i o n of t h e i n c o m i n g b e a m d
is m a g n i f i e d by a f a c t o r M to p r o d u c e t h e o u t g o i n g
b e a m d . a is t h e a s y m m e t r y a n g l e , i.e. t h e a n g l e
b e t w e e n crystal s u r f a c e a n d lattice p l a n e s . (B) By a n
a p p r o p r i a t e c o m b i n a t i o n of t w o a s y m m e t r i c diffraction
crystals C 1 a n d C 2 a t w o - d i m e n s i o n a l total m a g n i f i cation (the p r o d u c t of the linear m a g n i f i c a t i o n M) c a n
be o b t a i n e d .
i n
at
T h e w h o l e M S B e a m l i n e (wiggler s o u r c e , R h m i r r o r s ,
d o u b l e - c r y s t a l m o n o c h r o m a t o r a n d slits) w a s s i m u lated with t h e ray-tracing p r o g r a m S h a d o w [3]. For
c o l l i m a t e d b e a m delivery c o n f i g u r a t i o n , t h e a n g u l a r
d i v e r g e n c e F W H M at the e x p e r i m e n t d o e s not t r e s p a s s 2 0 u r a d , s e e Fig. 3. A c o m p a r i s o n with t h e relev a n t r o c k i n g c u r v e implies that the first Si (220) B r a g g
crystal will a c c e p t 9 5 % of t h e i n c o m i n g intensity. W i t h
this realistic s o u r c e distribution, the c o m p l e t e B r a g g
m a g n i f i e r h a s b e e n s i m u l a t e d . In t h e s i m u l a t i o n , t h e
b e a m is c o l l i m a t e d by a slit t o a 1 x 1 m m profile, j u s t
before i m p i n g i n g on t h e first crystal of t h e B r a g g M a g nifier. Fig. 4 s h o w s t h e final intensity distribution at t h e
locus of t h e detector. T h e results of the s i m u l a t i o n
s u g g e s t that with s u c h a s e t u p a linear m a g n i f i c a t i o n
of a f a c t o r of 30 in both d i m e n s i o n s is feasible.
2
C2
o u t
rocking
35
83
CHARACTERIZATION
Both S i ( 2 2 0 ) crystals h a v e b e e n c h a r a c t e r i z e d at the
Seifert station of the P S I , s e e Fig 5. T h e C u X - r a y
t u b e of the d e v i c e h a s b e e n run at 4 0 k e V a n d 4 0 m A ,
with a Ni filter for r e m o v i n g b r e m s s t r a h l u n g c o n t a m i nation. T h e m e a s u r e m e n t s h a v e b e e n d o n e in t h e
"high r e s o l u t i o n " c o n f i g u r a t i o n w h i c h i m p l i e s t h e u s e of
a multilayer mirror for c o l l i m a t i o n as well as a M R B C - 4
G e ( 4 4 0 ) m o n o c h r o m a t o r c o n s i s t i n g in t w o G e r m a n i u m
c h a n n e l cuts: the resulting b e a m d i v e r g e n c e w a s
a b o u t 5".
F i g . 3: M S - b e a m l i n e d i v e r g e n c e is less t h a n 2 0 u r a d
at t h e locus of t h e e x p e r i m e n t . A x i s ' s units are radians.
F i g . 5: S e t u p for t h e crystal c h a r a c t e r i z a t i o n at t h e
Seifert station. 1 . T u b e . 2. Multilayer. 3. M o n o c h r o m a t o r 4 . C r y s t a l . 5. Detector.
F i g . 4 : Intensity distribution in t h e final i m a g e p l a n e .
M a g n i f i c a t i o n is a b o u t a f a c t o r 3 0 . A x i s ' s units are c m .
C o n s e q u e n t l y t h e realization of the e x p e r i m e n t a l
s e t u p h a s b e e n s t a r t e d . T h e crystals h a v e b e e n prep a r e d in c o l l a b o r a t i o n w i t h t h e Institut für Kristallz ü c h t u n g , Berlin, with an a n g u l a r a c c u r a c y of a b o u t
o n e m i n u t e of arc a n d a s u r f a c e r o u g h n e s s of better
t h a n 1 | j m . After a high quality polishing of their b a c k side, t h e crystals h a v e b e e n fixed by optical c o n t a c t ing o n a high precision g l a s s s u p p o r t p e r f o r m e d by
Z e i s s . In this w a y , no m e c h a n i c a l d e f o r m a t i o n of t h e
crystals t h e m s e l v e s c a n occur. For e a c h crystal unit
the m e c h a n i c a l m o u n t i n g a l l o w s an
adjustment
a r o u n d e a c h rotation axis. T h e m o v e m e n t that c o r r e s p o n d s t o t h e B r a g g a n g l e c a n be p e r f o r m e d in s t e p s
of .05 a r c s e c t o c o p e with t h e v e r y n a r r o w r o c k i n g
c u r v e at 2 3 . 1 k e V (Fig. 2). In a d d i t i o n , t h e s e c o n d
crystal c a n be p o s i t i o n e d by m e a n s of a X Y - t a b l e [4].
0 -I
-12
1
-8
1
-4
1
1
0
4
1
1
8
12
ArcSeconds
F i g . 6: M e a s u r e d r o c k i n g c u r v e s of t h e S i ( 2 2 0 ) c r y s tals at 23.1 k e V .
84
W e m e a s u r e d t h e r o c k i n g c u r v e s of both crystals on
different p l a c e s of t h e s u r f a c e . T h e w i d t h s of t h e
measured rocking curves were comparable to the
theoretical c a l c u l a t i o n s , d e m o n s t r a t i n g that t h e crystals b e h a v e a l m o s t like ideal crystals. S o m e of t h e
results are g i v e n in Fig. 6.
DISCUSSION A N D OUTLOOK
After e x t e n s i v e s i m u l a t i o n s , S i ( 2 2 0 ) crystals h a v e
b e e n c h o s e n t o build t h e m a g n i f y i n g X - r a y optic of t h e
B r a g g M a g n i f i e r unit w h i c h will be installed at t h e
B e a m l i n e M S . It h a s b e e n s h o w n that m a g n i f i c a t i o n s
up t o 1 0 0 0 x c a n easily be r e a c h e d at e n e r g i e s well
a b o v e 2 0 k e V . T h e resulting m a g n i f i e d i m a g e c a n be
o b s e r v e d with t h e help of a s t a n d a r d X T M detector.
First e x p e r i m e n t a l t e s t s o n t h e p r e p a r e d c r y s t a l s pair
s h o w g o o d a g r e e m e n t with the t h e o r e t i c a l predictions.
Next s t e p s will be a d d i t i o n a l crystal c h a r a c t e r i z a t i o n s
( t o p o g r a p h i c a l investigation) a s well a s t h e integration
in t h e w h o l e X T M s y s t e m .
W e look f o r w a r d to p e r f o r m first
t e s t s in t h e first q u a r t e r of 2 0 0 2 .
synchrotron-based
REFERENCES
[1]
M. K u r i y a m a et al., Hard X-Ray Microscope
With
Submicrometer
Spatial Resolution,
J . R e s . Natl.
Inst. S t a n d . T e c h n o l . 9 5 , 5 5 9 ( 1 9 9 0 ) , pp. 5 5 9 574.
[2]
S. B r e n n a n , P. C o w a n , R e v . Sei. Instr. 6 3 , 8 5 0
(1992).
[3]
del Rio M. S a n c h e z , R. D e j u s , S P I E , vol. 3 4 4 8 ,
230(1998).
[4]
M. S t a m p a n o n i et al., Computer
Microtomography, PSI Scientific R e p o r t 2 0 0 0 , V o l u m e V I I ,
p. 8 1 .
85
SPIN-RESOLVED FERMI-SURFACE MAPPING ON Ni(111)
M. Hoesch,
M. Muntwiler (PSI / University
M. Hengsberger,
W. Auwärter,
of Zurich),
T. Greber,
V. N. Petrov (St. Petersburg
Techn.
J. Osterwalder
(University
of Zurich)
University)
First results from the spin-resolved
photoelectron
spectrometer
COPHEE
are presented.
The spin character of electronic
states at the Fermi level of nickel metal was measured
by angle-resolved
ultraviolet
photoelectron
spectroscopy
on the Ni(111) surface.
The direction
of sample magnetisation
was determined through the individual
components
of the polarisation
vector and polarimetry
of electrons
photoemitted from spin-split bands at the Fermi level directly revealed their spin
character.
INTRODUCTION
C O P H E E , the COmplete PHotoEmission Experiment
w a s n a m e d b e c a u s e it d e t e r m i n e s all p r o p e r t i e s of
the p h o t o e l e c t r o n s , e n e r g y , m o m e n t u m a n d spin [1].
It f e a t u r e s a full t h r e e - d i m e n s i o n a l e l e c t r o n s p i n - p o larimeter c o n s i s t i n g of t w o o r t h o g o n a l Mott d e t e c t o r s
mounted on a hemispherical electron energy analyser. A t w o - a x i s s a m p l e g o n i o m e t e r a l l o w s for
choosing any photoelectron emission angle above
the s u r f a c e . T h e i n s t r u m e n t w a s c o m p l e t e d in 2 0 0 1
a n d is currently o p e r a t e d s t a n d - a l o n e at the p h y s i c s
institute at Z u r i c h University u s i n g a high flux He
lamp.
Nickel is a s t r o n g f e r r o m a g n e t with a c o m p l e t e l y filled
majority d - b a n d . Its b a n d s t r u c t u r e is k n o w n f r o m calculations a n d a large s e t of a n g l e - r e s o l v e d p h o t o e l e c tron s p e c t r o s c o p y data [2]. In t h e s e data, t h e s p i n
c h a r a c t e r of individual b a n d s is inferred f r o m
c o m p a r i s o n with the c a l c u l a t i o n s a n d t h r o u g h the
o b s e r v a t i o n of spin-split b a n d s w h i c h s h o w identical
d i s p e r s i o n apart f r o m an e n e r g e t i c splitting. C O P H E E
a i m s at direct o b s e r v a t i o n of t h e s p i n c h a r a c t e r of
t h e s e b a n d s for (i) identification of spin-character, (ii)
quantitative p o l a r i m e t r y a n d (iii) a d d i t i o n a l c o n t r a s t
w h e r e different b a n d s o v e r l a p . T h e nickel s a m p l e
s e r v e s as a test c a s e for t h e a p p a r a t u s .
T H E Ni(111) S A M P L E
Macroscopic spin-polarimetry from a ferromagnet
requires a m a g n e t i s e d s a m p l e . In o r d e r t o a c h i e v e a
s i z e a b l e r e m n a n t m a g n e t i s a t i o n a n d t o r e d u c e stray
m a g n e t i c fields, t h e m a g n e t i c flux m u s t be kept inside
the s a m p l e . For this p u r p o s e , t h e s a m p l e is s h a p e d
as a c l o s e d f r a m e . T o fit t h e p i c t u r e - f r a m e s h a p e into
the limited s p a c e o n t h e s a m p l e holder, a d e s i g n w a s
made which closes the sample below the polished
(111) s u r f a c e (Fig. 1). T h e coil w o u n d a r o u n d t h e
b o t t o m part of the f r a m e is u s e d for heating with a
s m a l l D C c u r r e n t a n d for reversibly m a g n e t i s i n g the
s a m p l e by h i g h - c u r r e n t p u l s e s .
T h e ( 1 1 1 ) s u r f a c e of nickel b e a r s t h e difficulty that
the [111] e a s y axis of m a g n e t i s a t i o n is p e r p e n d i c u l a r
to t h e s u r f a c e a n d at t h e s a m e t i m e the s u r f a c e m a g netisation is m o s t l y in p l a n e . T h e m a g n e t i s a t i o n a l o n g
the s u r f a c e is a l s o f a v o u r a b l e for t h e e x p e r i m e n t b e c a u s e t h e p i c t u r e - f r a m e s h a p e c a n be e m p l o y e d . O u r
s a m p l e p r o v e d t o be r e m n a n t l y m a g n é t i s a b l e , h o w ever a s i n g l e d o m a i n state c o u l d not be a c h i e v e d .
a;
b)
F i g . 1 : Picture f r a m e N i ( 1 1 1 ) s a m p l e , (a) P h o t o g r a p h of t h e s a m p l e with t h e p o l i s h e d s u r f a c e o n the
left a n d t h e f i l a m e n t coil for heating a n d m a g n e t i s i n g
w o u n d a r o u n d the b o t t o m part of t h e s a m p l e f r a m e ,
(b) S c h e m a t i c d r a w i n g of t h e N i ( 1 1 1 ) picture f r a m e
s a m p l e a s m o u n t e d o n the s a m p l e holder. T h e a r r o w
indicates t h e m a g n e t i s a t i o n v e c t o r M.
MAGNETISATION DIRECTION AND MAGNITUDE
T h e t h r e e - d i m e n s i o n a l Polarimeter of C O P H E E a l l o w s for the d e t e r m i n a t i o n of t h e m a g n e t i s a t i o n v e c t o r
at a n y setting of the g o n i o m e t e r . E a c h of t h e t w o Mott
d e t e c t o r s m e a s u r e s a set of s c a t t e r i n g a s y m m e t r i e s ,
w h i c h are p r o p o r t i o n a l t o t h e polarisation c o m p o n e n t s
of the p h o t o e l e c t r o n s . T h e u s e of t w o Mott d e t e c t o r s
s p a n s all c o m p o n e n t s of t h e t h r e e d i m e n s i o n a l polaris a t i o n s p a c e . T o investigate the m a g n e t i c p r o p e r t i e s
of the s a m p l e w e p e r f o r m e d p o l a r i m e t r y of the s e c o n d a r y e l e c t r o n s e m i t t e d at 2 e V kinetic e n e r g y in norm a l e m i s s i o n u p o n excitation with U V light f r o m t h e
He l a m p . T h e s e e l e c t r o n s are p o l a r i s e d parallel t o t h e
s a m p l e m a g n e t i s a t i o n with a d e g r e e of polarisation of
a p p r o x . 8 % for a fully m a g n e t i s e d s a m p l e [3]. Fig. 2
s h o w s t h e m e a s u r e d a s y m m e t r i e s in t w o o r t h o g o n a l
Mott d e t e c t o r s a s a f u n c t i o n of t h e rotation a n g l e of
the s a m p l e . A t t h e m a x i m a of the s i n e - m o d u l a t e d
a s y m m e t r i e s the sensitive a x e s of the Mott d e t e c t o r s
m a t c h the m a g n e t i s a t i o n direction. T h e a m p l i t u d e of
the m o d u l a t i o n s h o w s that the s a m p l e m a g n e t i s a t i o n
is a p p r o x . 15 % t o 2 5 % of t h e s a t u r a t i o n m a g n e t i s a tion. Further details o n t h e interpretation are g i v e n in
[4]-
86
s e e n in 2 0 0 2 . T h e i n s t r u m e n t will t h e n benefit f r o m a
freely t u n e a b l e p h o t o n e n e r g y , w h i c h o p e n s t h e
c h o i c e of a n y /(-vector in b a n d - s t r u c t u r e m a p p i n g a n d
f r o m t h e flexibility in c h o o s i n g t h e light polarisation.
1500
1400
5L
8.
1300-
1200 -S
1100 -
0.5
0.0
F i g . 2 : Mott s c a t t e r i n g a s y m m e t r i e s as m e a s u r e d by
the t w o o r t h o g o n a l P o l a r i m e t e r s of C O P H E E (black
a n d w h i t e circles) for s e c o n d a r y e l e c t r o n s e m i t t e d at
2 e V in n o r m a l e m i s s i o n f r o m N i ( 1 1 1 ) . T h e s a m p l e
w a s rotated ((p-angle) a b o u t t h e s a m p l e n o r m a l t o
v a r y the in-plane m a g n e t i s a t i o n direction.
SPIN-RESOLVED FERMI-SURFACE MAPPING
T h e F e r m i - s u r f a c e of Nickel f e a t u r e s s h e e t s d u e t o
minority d - b a n d s a n d a large s p - b a n d e l e c t r o n surf a c e . O n the N i ( 1 1 1 ) s u r f a c e , a pair of spin-split s p b a n d s is s e e n a r o u n d t h e [-1-1 2] a z i m u t h with a pair
of d - b a n d s near by. In this g e o m e t r y , the t w o Mott
detectors
measure the spin-polarisation
almost
e q u i v a l e n t l y a n d a direct c r o s s c h e c k i n g is p o s s i b l e .
Fig. 3 s h o w s s p i n - r e s o l v e d p h o t o e m i s s i o n d a t a . T h e
s p i n - c h a r a c t e r of the b a n d is clearly r e v e a l e d t h r o u g h
the sign of the Mott d e t e c t o r a s y m m e t r y . T h e t w o
asymmetry curves were measured quasi-simultan e o u s l y by 2 Hz s w i t c h i n g b e t w e e n t h e t w o d e t e c t o r s .
T h e y fall precisely o n t o p of e a c h other.
-0.5
-1.0
-1.5
1
-40
0
20
r
40
Angle <p (deg.)
F i g . 3:
Spin-resolved
photoemission
data
from
N i ( 1 1 1 ) e x c i t e d with Hel ( h v = 2 1 . 2 e V ) . T h e u p p e r
part s h o w s t h e p h o t o e l e c t r o n intensity a n d t h e lower
part t h e m e a s u r e d a s y m m e t r y as a f u n c t i o n of the
a z i m u t h a l e m i s s i o n a n g l e <p near g r a z i n g e m i s s i o n .
Black a r r o w s m a r k t h e k n o w n a s s i g n m e n t of t h e
p e a k s t o (minority) d - b a n d s a n d spin-split s p - b a n d s .
Data f r o m t w o Mott d e t e c t o r s are s h o w n by black a n d
white squares.
REFERENCES
[1]
M. H o e s c h et al., PSI Scientific
Volume VII.
[2]
T . J . K r e u t z et al., P h y s . Rev. B 5 8 ( 1 9 9 8 ) 1 3 0 0
and references therein
[3]
M. L a n d o l t in P o l a r i z e d E l e c t r o n s in S u r f a c e S c i e n c e , e d . R. F e d e r W o r l d Scientific, 1 9 8 5
[4]
M. H o e s c h et al., s u b m i t t e d t o J . E l e c t r o n S p e c trosc. Rel. P h e n .
CONCLUSION AND OUTLOOK
T h e d a t a p r e s e n t e d in this a n n u a l report s h o w that
C O P H E E p e r f o r m s to e x p e c t a t i o n a n d d e m o n s t r a t e
its capability t o m e a s u r e s p i n - r e s o l v e d F e r m i - s u r f a c e
data a n d t o d e t e r m i n e t h e direction of s p i n - p o l a r i s a tion. T h e e x p e r i m e n t w a s o p e r a t e d s t a n d - a l o n e u s i n g
a high-flux He l a m p . T r a n s f e r of the a p p a r a t u s to t h e
s e c o n d port of t h e S I S b e a m l i n e at t h e S L S is f o r e -
-20
I
Report
2000,
87
SCIENTIFIC REPORTS
88
DIRECT OBSERVATION OF CHARGE ORDER IN EPITAXIAL FILM OF NdNi0
3
U. Staub, G.I. Meijer (IBM-Rueschlikon),
F. Fauth (ESRF),
R. Allenspach
(IBM-Rueschlikon),
J. G. Bednorz,
J. Karpinski,
S.M. Kazakov (ETHZ),
L. Paolasini, F. d'Acapito
(ESRF)
The first direct observation
of charge order of M
' and Ni
by resonant X-ray scattering
experiments
in
an epitaxial film of NdNi0
is reported. A quantitative
value of 6+ & = 0.45 ± 0.04 e was obtained.
The
temperature
dependence
of the charge order deviates significantly
from those of the magnetic
moment
and crystallographic
structure.
This might be an indication
of a difference
in their fluctuation
time scales.
These observations
are discussed
in terms of the temperature-driven
metal-insulator
transition
in the
RN1O3 family.
3 + < 5
3-8
3
O n e of t h e l o n g - s t a n d i n g i s s u e s a s s o c i a t e d with
s t r o n g l y c o r r e l a t e d e l e c t r o n s y s t e m s is the m i c r o s c o p i c origin of the metal-to-insulator transitions a n d
the n a t u r e of the g r o u n d state. A p r o t o t y p e b a n d w i d t h controlled
metal-insulator
transition
is
RNi0
3
(R=La
Lu or Y ) with distorted p e r o v s k i t e structure.
T h e n o m i n a l v a l e n c e of Ni is 3+ with d-electron c o n figuration t e
a n d spin S = 1/2. R N i 0 h a s a s m a l l
c h a r g e - t r a n s f e r e n e r g y a n d c a n be r e g a r d e d a s a selfd o p e d Mott insulator. N d N i 0 exhibits a t h e r m a l l y driven m e t a l - i n s u l a t o r transition at a n d a further t r a n sition t o l o n g - r a n g e a n t i f e r r o m a g n e t i c T | =T = 2 0 0 K.
A s s o c i a t e d with T is a slight but a b r u p t e x p a n s i o n of
the c r y s t a l l o g r a p h i c unit cell, w h i c h c a u s e s a n a r r o w ing of t h e b a n d w i d t h , e v e n t u a l l y l e a d i n g t o t h e o p e n ing of a g a p at t h e F e r m i s u r f a c e .
6
2 g
1
g
3
3
M
N
m
Resistivity m e a s u r e m e n t s of the 500-Â-thick N d N i 0
film s h o w s a first-order m e t a l - i n s u l a t o r transition at
a p p r o x i m a t e l y 170 K. T h e r e s o n a n t X - r a y scattering
e x p e r i m e n t s ( I D 2 0 , E S R F ) f o c u s e d on reflections of
t y p e (Ohl) a n d (hOI), with h a n d I o d d . In Pbnm s y m metry, t h e s e reflections h a v e no c o n t r i b u t i o n f r o m the
Ni site. Fig. 1 s h o w s t h e e n e r g y d e p e n d e n c e of the
(105) a n d ( 0 1 5 ) reflections. T h e s p e c t r u m of the ( 1 0 5 )
s h o w s a s t r o n g m a x i m u m [ m i n i m u m for (015)] at
8 3 4 4 e V , a p p r o x i m a t e l y 10 e V a b o v e t h e Ni K - e d g e
( 8 3 3 3 e V ) . T h i s s h o w s that t h e s e reflections c o n t a i n a
significant contribution f r o m t h e electronic s t a t e s of
the Ni ions. A b o v e T i , t h e scattering is i n d e p e n d e n t
of the e n e r g y , a n d t h e r e n o l o n g e r is a r e s o n a n t c o n tribution f r o m Ni.
3
scattering f a c t o r s of t h e Nil a n d N i sites are o b t a i n e d .
T h e e n e r g y shift b e t w e e n t h e N i a n d Ni -site scattering f a c t o r s at t h e Ni K-edge is f o u n d t o be
0.90 ± 0.08 e V , w h i c h relates to a c h a r g e o r d e r of
Ô+ & = 0.42 ± 0.04 e in t h e g r o u n d state. X A S s p e c t r o s c o p y f o u n d that t h e Ni a v e r a g e e l e c t r o n i c state is
a m i x t u r e of a p p r o x i m a t e l y 7 0 % 3 d a n d 30 % 3 d L ,
c o r r e s p o n d i n g t o Ni| a n d N i v a l e n c e s of a p p r o x i m a t e l y 3+ a n d 2 . 5 + , r e s p e c t i v e l y
0 a n d 6~ 0.5 e).
M
r
M
7
8
M
T h e c h a r g e - o r d e r o r d e r p a r a m e t e r c a n be e x t r a c t e d
f r o m the t e m p e r a t u r e d e p e n d e n c e of t h e integrated X ray intensity of the ( 1 0 5 ) reflection. T h e structural a n d
m a g n e t i c o r d e r p a r a m e t e r s are identical, t h e c h a r g e o r d e r o r d e r p a r a m e t e r , h o w e v e r , b e h a v e s differently.
T h i s m a y indicate a difference in t h e f l u c t u a t i o n t i m e
s c a l e s of t h e m a g n e t i c m o m e n t a n d structure a s c o m pared to the charge.
In c o n c l u s i o n , w e directly o b s e r v e c h a r g e o r d e r ( N i
a n d N i ) at the m e t a l - i n s u l a t o r transition in N d N i 0
with Ni, is 3 d a n d N i a 5 0 % m i x t u r e of 3 d a n d 3 d L .
3 + 8
3 - 5
3
7
7
M
8
11.0 r"">—i—i—i—i—i—i—i—i—I—i—i—i—1—g—i—1—1—1—g—i—i—i—i—i 2.0
M
T h e structure f a c t o r of the ( 0 1 5 ) a n d ( 1 0 5 ) reflections
c o n t a i n s differences of t w o Ni sites w h e n t h e s y m m e try is l o w e r e d b e l o w T | . A n e n e r g y d e p e n d e n c e of t h e
B r a g g reflections at t h e Ni K-edge o n l y o c c u r s w h e n
the c o r r e s p o n d i n g scattering f a c t o r s of t h e s e t w o sites
are different. T h e r e f o r e , our data directly p r o v e that
N d N i 0 h a s a l o n g - r a n g e c h a r g e - o r d e r e d g r o u n d state
with t h e t w o distinct Ni sites, N i ' a n d N i .
M
7.5
r
8330
1
8340
1
8350
8360
8370
1.0
8380
3
3 + 8
energy (eV)
3 - 5
R e s o n a n t X - r a y scattering in c o m b i n a t i o n with X - r a y
a b s o r p t i o n ( X A S ) is u s e d t o d e t e r m i n e t h e size of this
c h a r g e o r d e r a n d t h e site-selective electronic structure
of t h e Ni ions. W i t h use of the K r a m e r s - K r o n i g relation, t h e site-selective real a n d i m a g i n a r y parts of t h e
F i g . 1 : E n e r g y d e p e n d e n c e of the ( 1 0 5 ) a n d ( 0 1 5 )
reflections of N d N i 0 with c - c polarization in the insulating state at 2 0 K.
3
89
STRUCTURAL DISORDER BELOW THE METAL-INSULATOR TRANSITION IN
CA Ru0
2
U. Staub,
B. Schmitt,
F. Gozzo,
T. Bortolamedi,
P. Pattison
(University
4
K. Conder,
C. Hörmann
of Lausanne),
D.
(University
of
Erlangen),
Sheptyakov
Results of powder diffraction
(X-ray and neutron) on Ca Ru0
are reported. Unusual line shapes h,k,l, depending broadenings
of reflections
are observed below the metal insulator transition.
This is interpreted
in
terms of a slight oxygen non-stochiometry
leading to different electronic
regions and correspondingly
regions of different structural
distortions.
2
Layered perovskite ruthenates have attracted conside r a b l e interest s i n c e t h e d i s c o v e r y of s u p e r c o n d u c t i v ity in S r R u 0 , t h e o n l y isostructural a n a l o g u e t o t h e
high-Tc m a t e r i a l s a n d p r o p o s e d p - w a v e s u p e r c o n ductor. T h e s u b s t i t u t i o n of S r b y C a l e a d s t o rather
different p h y s i c a l p r o p e r t i e s . C a R u 0 is a Mott i n s u lator w i t h a t h e r m a l d r i v e n m e t a l - i n s u l a t o r transition at
T i = 3 4 0 K, s t r o n g l y d e p e n d e n t o n t h e e x a c t o x y g e n
s t o c h i o m e t r y . A s s o c i a t e d w i t h T i is a first-order
structural p h a s e transition w i t h significant c h a n g e s in
the lattice c o n s t a n t s .
2
4
2
4
M
M
4
Fig. 2 s h o w s a s e c t i o n of a h i g h - r e s o l u t i o n pattern
t a k e n at the S w i s s N o r w e g i a n b e a m l i n e at t h e E S R F .
A r e a s o n a b l e m o d e l t o d e s c r i b e t h e p e a k s h a p e is to
i n t r o d u c e u n c o r r e l a t e d strain w i t h a t r i a n g u l a r d i s t r i b u tion of d - s p a c i n g s , w h i c h is a rather u n u s u a l c a s e .
S u c h a s i m p l e m o d e l c a n qualitatively d e s c r i b e t h e
p e a k s h a p e s a n d b r o a d e n i n g s o b s e r v e d in t h e h i g h r e s o l u t i o n p a t t e r n . T h e o b s e r v e d strain is likely a s s o ciated with a small oxygen non-stochiometry, which
effects "locally" t h e e l e c t r o n i c s t r u c t u r e a n d l e a d s to a
distribution of T
a n d c o r r e s p o n d i n g t o a distribution
of lattice distortions. O x y g e n i n d u c e d d i s o r d e r (strain)
h a s b e e n f o u n d in h i g h - T s u p e r c o n d u c t o r s P b S r Y i _
C a C u 0 [1] a n d a n o r d e r e d distortions are f o u n d in
t h e i n c o m m e n s u r a t e B Í 2 2 1 2 s u p e r c o n d u c t o r s [2]. T o
o b t a i n m o r e i n f o r m a t i o n o n the o x y g e n n o n - s t o chiometry, w e have performed high-resolution neutron
diffraction e x p e r i m e n t s at H R P T at S I N Q . T h e s t u d y of
t h e t e m p e r a t u r e d e p e n d e n c e of t h e distortion will a l l o w u s t o get m o r e insight in t h e v e r y u n u s u a l structural a n d e l e c t r o n i c b e h a v i o u r . F u r t h e r a n a l y s i s a n d
e x p e r i m e n t s are in p r o g r e s s .
M !
Fig. 1 s h o w s a s m a l l s e c t i o n of t h e X - r a y diffraction
pattern of C a R u 0 t a k e n w i t h t h e n e w l y d e v e l o p e d
strip d e t e c t o r at the S L S M a t e r i a l s S c i e n c e b e a m l i n e .
T h e pattern e x h i b i t s n a r r o w lines a b o v e T , w h i c h shift
significantly a n d b r o a d e n w h e n g o i n g t h r o u g h T | . T h e
reflections h a v e s t r a n g e h,k,l, d e p e n d e n t line s h a p e s
a n d b r o a d e n i n g s , w h i c h c a n n o t be e x p l a i n e d s i m p l y
b y a G a u s s i a n distribution of lattice strain.
2
4
M
M
c
x
x
3
2
2
8
Ca,Ru0
. I.... I... H,
4
-1—n—i—i—j—i—n—i—\—i—i—i—r-|—i—i—i—i—|—n—i—r~\-
Ca Ru0
295 K
2
4800
4
4000
28.0
28.5 29.0 29.5 30.0 30.5 31.0 31.5 32.0
20 (°)
F i g . 2 : Diffraction pattern of C a R u 0
2
4
t a k e n at t h e
S N B L of the E S R F (line; t r i a n g u l a r m o d e l ) .
F i g . 1 : Diffraction pattern of C a R u 0 t a k e n w i t h t h e
strip d e t e c t o r at t h e M a t e r i a l s S c i e n c e b e a m l i n e
(SLS).
2
4
REFERENCES
[1]
U. S t a u b et al., P h y s . Rev. B 5 7 , 5 5 3 5 ( 1 9 9 8 ) .
[2]
A. Y a m a m o t o et al., P h y s . , Rev. B 4 2 ,
4 2 2 8 (1990).
90
PROPAGATION OF A FOCUSED X-RAY BEAM WITHIN A PLANAR X-RAY
WAVEGUIDE
J.H.H. Bongaerts,
C. David,
G.H. Wegdam
H. Keymeulen,
(University
of Amsterdam),
M. Drakopoulos
T. Lackner, J.F. van der Veen
(PSI/ETHZ)
Recently w e
have developed a tunable
x-ray
w a v e g u i d e [1,2] t o p e r f o r m d y n a m i c a n d static x-ray
diffraction e x p e r i m e n t s o n thin fluids c o n f i n e d within
the g u i d i n g layer of t h e w a v e g u i d e . T h e typical
w a v e g u i d e g a p s are b e t w e e n 5 0 n m a n d a f e w
m i c r o n s . S i n c e the s c a t t e r i n g v o l u m e d e c r e a s e s at
decreasing gap width and the
electron-density
c o n t r a s t is v e r y s m a l l for s o m e v e r y interesting
s y s t e m s , t h e s c a t t e r e d intensity c a n be e x t r e m e l y low.
In o r d e r t o e n h a n c e t h e flux inside t h e w a v e g u i d e , w e
u s e d a o n e - d i m e n s i o n a l t r a n s m i s s i o n Fresnel z o n e
plate ( F Z P ) lens to f o c u s x rays of an e n e r g y of
13.3 k e V o n t o t h e e n t r a n c e of our x - r a y w a v e g u i d e .
T h e rays are incident f r o m the side u n d e r a g r a z i n g
a n g l e (Fig. 1). Fig. 2 s h o w s a s c a n n i n g e l e c t r o n
m i c r o g r a p h of the F Z P - l e n s . T h e structure w a s patt e r n e d by u s e of e l e c t r o n b e a m l i t h o g r a p h y a n d
s u b s e q u e n t w e t c h e m i c a l e t c h i n g of a < 1 1 0 >-oriented
silicon s u b s t r a t e , a l l o w i n g for a high a s p e c t ratio of t h e
o u t e r F r e s n e l z o n e s . T h e height of the ridges is
5.5 urn.
At 13.3 k e V , t h e path length difference b e t w e e n t h e
t r e n c h e s a n d ridges s h o u l d be 16.8 urn in o r d e r to o b tain a p h a s e shift TT w h i c h yields the m a x i m u m effic i e n c y of the lens. By rotating t h e orientation of t h e
lens by 7 0 . 9 d e g r e e s , w e c a n t u n e this p a t h length
difference t o this o p t i m a l c o n d i t i o n . T h e tunability of
the lens m a k e s t h e lens suitable for a large e n e r g y
r a n g e . T h i s m e t h o d is d e s c r i b e d in ref. [3]. W e f o u n d
an e x p e r i m e n t a l lens efficiency of 3 2 . 6 %, w h i c h is
c o m p a r a b l e to t h e m a x i m u m theoretical efficiency for
a perfect lens of 37.4 % w h e n t a k i n g a b s o r p t i o n into
account.
(ESRF),
In
Fig. 3, t h e
transmitted
intensity
through
a
w a v e g u i d e of 3 0 0 n m w i d t h is s h o w n as a f u n c t i o n of
the
vertical
lens
position. T h e
maximum
flux
e n h a n c e m e n t inside t h e w a v e g u i d e is a factor 54 a n d
t h e F W H M is 1.03 urn. T h i s w i d t h c o r r e s p o n d s t o the
gain f a c t o r 54, if a G a u s s i a n s h a p e of t h e i m a g e at the
w a v e g u i d e is a s s u m e d . In Fig. 4 , t h e n u m e r i c a l l y
c a l c u l a t e d a n d t h e m e a s u r e d far field intensity
distributions l(0j,0 )
are s h o w n as a f u n c t i o n of
i n c i d e n c e a n g l e 0, a n d exit a n g l e 0 - T h e w a v e g u i d e
g a p w i d t h is 9 5 7 n m . T h e different w a v e g u i d e m o d e s
s h o w up as m a x i m a a l o n g the d i a g o n a l . T h e
horizontal w i d t h of the d i a g o n a l c o r r e s p o n d s to t h e
a n g u l a r distribution e x p e c t e d f r o m t h e lens height a n d
focal l e n g t h . A l s o , a l o n g t h e d i a g o n a l a w e a k beating
period c a n be s e e n , w h i c h is indicative of m u l t i m o d e
interference. T h i s r e d u c e d visibility is a n indication
that t h e b e a m is partially c o h e r e n t . T h e vertical
t r a n s v e r s e c o h e r e n c e length in o u r situation w a s
8 0 m i c r o n s at the position of the lens, w h i c h itself is
2 0 0 m i c r o n h i g h . At large w a v e g u i d e w i d t h s , t h e i n t e n sity in t h e w a v e g u i d e is not fully c o h e r e n t , w h i l e at
g a p s m u c h s m a l l e r t h a n 3 5 0 n m (the o u t e r m o s t z o n e
w i d t h ) , t h e intensity is fully c o h e r e n t in t h e vertical
direction.
e
e
T h e results of this e x p e r i m e n t s h o w that it is p o s s i b l e
t o e n h a n c e t h e flux inside a p l a n a r w a v e g u i d e by a
f a c t o r 5 4 , a n d at g a p settings b e l o w the o u t e r m o s t
z o n e w i d t h , t h e intensity is still fully c o h e r e n t . T h i s
enables
a large r a n g e of c o h e r e n t
scattering
e x p e r i m e n t s to be p e r f o r m e d in s m a l l s c a t t e r i n g
v o l u m e s at greatly e n h a n c e d flux.
Standing wave
i
FZP lens
Waveguide entrance
F i g . 1 : S c h e m a t i c of the e x p e r i m e n t a l s e t u p . T h e
F Z P - l e n s f o c u s e s a 2 0 0 m i c r o n incident b e a m into a
c a . 1 m i c r o n size s p o t at t h e e n t r a n c e of t h e
w a v e g u i d e , w h e r e t h e w a v e g u i d e m o d e s are e x c i t e d .
By rotating t h e lens a r o u n d its axis, t h e p h a s e shift
b e t w e e n t h e t r e n c h e s a n d ridges c a n be t u n e d t o t h e
d e s i r e d t h e p h o t o n e n e r g y . T h e focal length of the
lens is 74 c m at 13.3 k e V .
F i g . 2 : Electron m i c r o g r a p h of a o n e - d i m e n s i o n a l
z o n e plate lens, w h i c h is u s e d t o f o c u s t h e b e a m . T h e
lens c o n s i s t s of a r e c t a n g u l a r pattern of t r e n c h e s a n d
ridges o n a 5 urn thick silicon m e m b r a n e . T h e
o u t e r m o s t z o n e w i d t h is 3 5 0 n m . T h e height of t h e
ridges is 5.5 urn. T h e lens s i z e p e r p e n d i c u l a r t o the
stripes is 2 0 0 urn a n d a l o n g t h e stripes 2.5 m m .
91
REFERENCES
0.000
0.005
0.010
0.015
z-position (mm)
0.020
F i g . 3:
Total
transmitted
intensity
through
the
w a v e g u i d e as a f u n c t i o n of t h e vertical lens position z
for a w a v e g u i d e
gap
W=300 nm. The
profile
r e p r e s e n t s t h e i m a g e of the u n d u l a t o r
source,
c o n v o l u t e d w i t h the g a p w i d t h of the w a v e g u i d e a n d
the diffraction limited resolution of the F Z P lens.
F i g . 4 : T h e intensity distribution in t h e far field /(0,,0 )
as a f u n c t i o n of i n c i d e n c e a n g l e 0, a n d exit a n g l e 0
for a 9 5 7 n m w a v e g u i d e g a p with a p r e - f o c u s e d
b e a m . T o the left is s h o w n a n u m e r i c a l calculation for
a partially c o h e r e n t b e a m , as e x p e c t e d f r o m t h e b e a m
properties. T o t h e right a r e s h o w n t h e e x p e r i m e n t a l
data. T h e b r o a d e n e d d i a g o n a l is c a u s e d by t h e
a n g u l a r distribution in t h e c o n v e r g i n g f o c u s e d w a v e s .
e
e
[1]
M.J. Z w a n e n b u r g ,
H.G. Ficke,
H. N e e r i n g s ,
J . F . v a n der V e e n , Rev. Sei. I n s t r u m . 7 1 , 1 7 2 3
(2000).
[2]
M.J. Z w a n e n b u r g , J . F . P e t e r s , J . H . H . B o n g a e r t s ,
S.A. d e V r i e s , D.L. A b e r n a t h y , J . F . v a n d e r V e e n ,
P h y s . Rev. Lett. 8 2 , 1 6 9 6 ( 1 9 9 9 ) .
[3]
C. D a v i d , B. N o e h a m m e r , E. Ziegler, A p p l . P h y s .
Lett. 7 9 , 1 0 8 8 ( 2 0 0 1 ) .
92
DYNAMICS OF CONFINED COLLOIDS
J.H.H. Bongaerts,
U. Flechsig,
J. Miguel (University
J.F. van der Veen
of
Amsterdam),
(PSI/ETHZ)
We have performed
x-ray photon correlation
spectroscopy
(XPCS) experiments
on colloidal
which are confined within a planar x-ray waveguide.
We observed
that the confinement
induces
time non-exponential
decay of the time correlation
function
<l(0)l(t)>.
INTRODUCTION
S u s p e n s i o n s of colloidal particles in a liquid s h o w a
p h a s e b e h a v i o u r that in a n u m b e r of r e s p e c t s is similar t o that of m o l e c u l a r liquids a n d solids [1]. T h e COLloid m a y b e fluid, crystalline or glassy, d e p e n d i n g o n
the particle v o l u m e c o n c e n t r a t i o n a n d t h e s t r e n g t h
a n d r a n g e of the interaction potential. In a d d i t i o n , t h e
p r e s e n c e of c o n f i n i n g w a l l s h a s t o b e t a k e n into c o n s i d e r a t i o n . A single wall i n d u c e s an o r d e r i n g of the
colloidal particles in layers parallel to the w a l l , t w o o p p o s i n g w a l l s at s m a l l d i s t a n c e E N H A N C E this layering
effect [2]. In g e n e r a l , t h e structure of a fluid is m o d i f i e d
in a n a r r o w g a p b e t w e e n t w o s u r f a c e s . T h i s h a s farREACHING c o n s e q u e n c e s for the lubricating
and
THEOLOGICAL p r o p e r t i e s of S U C H f l u i d s .
Directly related t o the structural m o d i f i c a t i o n s are
c h a n g e s in t h e d y n a m i c properties of the fluid. T h e
c o n f i n e m e n t is e x p e c t e d t o s l o w d o w n t h e particle
diffusion in t h e directions parallel a n d p e r p e n d i c u l a r t o
the w a l l s [3]. W a l l - i n d u c e d c h a n g e s in t h e h y d r o d y n a m i c f l o w field a r o u n d t h e particles a n d / o r structural
r e a r r a n g e m e n t s within t h e colloid m a y be r e s p o n s i b l e .
H o w e v e r , direct e x p e r i m e n t a l e v i d e n c e for t h e s e
m e c h a n i s m s is lacking. W e h a v e d e v e l o p e d a n e w
m e t h o d of d e t e c t i n g structural r e a r r a n g e m e n t s within
c o n f i n e d fluids (Fig. 1) [2]. It e m p l o y s t h e w a v e g u i d i n g
of x - r a y s within t h e g a p b e t w e e n t h e c o n f i n i n g surf a c e s . A t t h e e n t r a n c e of t h e p l a n a r w a v e g u i d e a single t r a n s v e r s e electric ( T E ) m o d e is e x c i t e d . T h e d e n sity v a r i a t i o n s within t h e fluid t h e n give rise to c o h e r ent s c a t t e r i n g into o t h e r m o d e s . By m e a s u r i n g t h e
distribution of t h e intensity s c a t t e r e d into t h e different
m o d e s , o n e d e r i v e s t h e d e n s i t y profile a c r o s s t h e g a p
b e t w e e n t h e plates. W e h a v e d e m o n s t r a t e d the validity of this a p p r o a c h for colloidal s u s p e n s i o n s of small
silica particles c o n f i n e d w i t h i n a g a p of a f e w h u n d r e d
nanometers.
Recently, w e e x t e n d e d o u r i n - w a v e g u i d e s t u d i e s t o
the t i m e d o m a i n , by p e r f o r m i n g x - r a y p h o t o n c o r r e l a tion s p e c t r o s c o p y ( X P C S ) m e a s u r e m e n t s o n t h e c o n fined c o l l o i d . T i m e correlation f u n c t i o n s w e r e m e a s ured for fixed m o m e n t u m t r a n s f e r q p e r p e n d i c u l a r to
the w a v e g u i d e p l a n e , c o r r e s p o n d i n g to specific
w a v e g u i d e m o d e s , a n d as a f u n c t i o n of q in t h e p l a n e
of the w a v e g u i d e . T h e m e a s u r e m e n t s w e r e p e r f o r m e d
at b e a m l i n e I D 1 0 A of E S R F , G r e n o b l e . M o n o d i s p e r s e
silica s p h e r e s of 2 1 0 n m d i a m e t e r w e r e d i s s o l v e d in a
w a t e r - g l y c e r o l m i x t u r e h a v i n g a viscosity of 3 c P . T h e
s u s p e n s i o n , h a v i n g a v o l u m e c o n c e n t r a t i o n of 7 % ,
w a s c o n f i n e d b e t w e e n t w o flat silica s u r f a c e s w h i c h
f o r m the b o u n d a r i e s of the x - r a y w a v e g u i d e . T h e
particles
a long-
length of the w a v e g u i d e w a s 5 m m . W e s e l e c t e d an
e n e r g y of 13.2 k e V with a S i ( 1 1 1 ) m o n o c h r o m a t o r . A
t r a n s v e r s e l y c o h e r e n t b e a m w a s s e l e c t e d by a 8 m i c r o n pinhole. T h e s c a t t e r i n g v e c t o r in all e x p e r i m e n t s
b e l o w is in t h e plane of the c o n f i n i n g s u r f a c e s (Fig. 1 ).
A t g a p s b e l o w 2.5 m i c r o n s , w e o b s e r v e d l o n g - t i m e
tails in t h e correlation f u n c t i o n s at small m o m e n t u m
transfer. W e c h e c k e d w h e t h e r t h e s e tails w e r e i n d e e d
c a u s e d by t h e c o n f i n e m e n t by c h a n g i n g t h e path
length t h r o u g h t h e w a v e g u i d e . T h i s w a s d o n e by
t r a n s l a t i n g the w a v e g u i d e p e r p e n d i c u l a r t o t h e b e a m
(Fig. 1). In this w a y t h e path length t h r o u g h t h e
w a v e g u i d e relative t o that in t h e collar ( a l m o s t 1 m m
w i d e ) a r o u n d t h e c o n f i n e m e n t a r e a is c h a n g e d . W e
f o u n d that t h e l o n g t i m e tail d i s a p p e a r e d a s w e m o v e d
further a w a y f r o m the c e n t e r of the w a v e g u i d e . T h i s is
proof that t h e l o n g - t i m e tail is c a u s e d by the
w a v e g u i d e . T o g e t h e r with t h e fact that t h e long t i m e
tail is q - d e p e n d e n t , this is s t r o n g e v i d e n c e that w e are
not looking at a n e x p e r i m e n t a l artefact.
Fig. 2 s h o w s c o r r e l a t i o n f u n c t i o n s m e a s u r e d for t h r e e
different g a p settings at a single in-plane m o m e n t u m
t r a n s f e r (q//= 4 . 6 5 10" n m " ) . A s the g a p is d e c r e a s e d ,
t h e correlation f u n c t i o n s d e c r e a s e s l o w e r a n d d e v i a t e
m o r e f r o m a single e x p o n e n t i a l d e c a y . H e n c e , w e s e e
a clear effect of c o n f i n e m e n t o n t h e mobility of partic l e s in the plane of the s u r f a c e s . H y d r o d y n a m i c eff e c t s as well as structural c h a n g e s within t h e c o n f i n i n g
s p a c e m a y play a role. A n a l y s i s is in p r o g r e s s .
3
1
±
/ ;
F i g . 1 : T o p v i e w (top) a n d side v i e w ( b o t t o m ) of t h e
scattering g e o m e t r y . T h e dark a r e a r e p r e s e n t s the
fluid. T h e fluid f o r m s a collar a r o u n d t h e c o n f i n e d
a r e a . T h i s results in a s u p e r p o s i t i o n of t h e s c a t t e r i n g
f r o m t h e c o n f i n e d fluid w i t h that f r o m the bulk fluid.
T h e total length t h r o u g h t h e fluid with collar is c a .
6.5 m m , w h i l e t h e m a x i m u m w a v e g u i d e length is
5 mm.
93
REFERENCES
•
i i 11 lili)
10"
2
i i i 11 inj
10"
1
10°
i i 111 inj
i i 11 ilia;
i i 11 ilia;
10
10
Time (ms)
1
10
2
i i 11 lili)
10
3
i i 11 ini|
10
4
5
F i g . 2 : T i m e correlation f u n c t i o n s g - 1 for different g a p
s e t t i n g s W , m e a s u r e d at q = 4 . 6 5 10 " n m " . T h e dyn a m i c s p e c k l e c o n t r a s t w a s typically 4 0 %. For c o m p a r i s o n , t h e correlation f u n c t i o n s h a v e b e e n n o r m a l ized t o o n e .
2
fí
3
1
A s t h e g a p is c l o s e d , t h e correlation f u n c t i o n d e c a y s
slower. A t t h e s m a l l e s t g a p of 7 0 0 n m w i d t h , t h e d e c a y t i m e is a f a c t o r 3 longer t h a n at a g a p of
1.3 m i c r o n w i d t h . For a bulk fluid, t h e correlation f u n c tions c a n be fitted t o a single e x p o n e n t i a l d e c a y . W i t h
the f u n c t i o n s s h o w n h e r e , this is not p o s s i b l e . A single
e x p o n e n t i a l fit w a s m a d e to the first part of t h e
W = 1 . 8 urn correlation f u n c t i o n in o r d e r to d e m o n s t r a t e
the d e v i a t i o n .
[1]
S e e e.g., W . K . K e g e l , A. v a n B l a a d e r e n , S c i e n c e
287, 291 (2000).
[2]
M.J. Z w a n e n b u r g , J . H . H . B o n g a e r t s , J . F . P e t e r s ,
D.O. Riese a n d J . F . v a n der V e e n ; P h y s . Rev.
Lett. 8 5 , 5 1 5 4 ( 2 0 0 0 ) .
[3]
I. P a g o n a b a r r a g a ,
M.H.J. Hägen,
C P . Lowe,
D. F r e n k e l , P h y s . R e v . E 5 9 , 4 4 5 8 ( 1 9 9 9 ) .
94
TIME-RESOLVED EXAFS WITH SINGLE X-RAY PULSES AT 1 KHZ
C. Bressler,
M. Chergui, F. Van Mourik (University
of
M. Saes (PSI, University of
Lausanne),
R. Abela, D. Grolimund,
(PSI),
R.W. Falcone,
S.L. Johnson,
A.M. Lindenberg
(UC
P.A. Heimann,
R.W. Schoenlein
(ALS)
Lausanne),
Berkeley),
We have performed
test experiments
at the Femtosecond
X-Ray Beamline 5.3.1 (ALS) to assess its utility
for studying condensed
phase dynamics
in liquids using X-ray absorption.
The pump-probe
scheme
is
applied with a fs-laser (pump) and hard X-ray pulses (probe). We have improved
the setup to allow efficient single pulse laser excitation
as well as low-noise X-ray detection up to 3.2 kHz repetition rate while
maintaining
spatial overlap in situ between
both beams. The discussed
scheme
will soon allow
pumpprobe experiments
on a wide class of systems with picosecond
(current SR pulse width) and
femtosecond
resolution at the future time-sliced
beamline for microdiffraction
and XAS at the SLS.
INTRODUCTION
W e are currently d e v e l o p i n g a s c h e m e to exploit
p u l s e d x - r a y for structural d y n a m i c s s t u d i e s at b e a m line 5.3.1 via t i m e - r e s o l v e d X - r a y a b s o r p t i o n ( E X A F S
and X A N E S ) techniques. X-ray absorption (XAS)
t e c h n i q u e s , s u c h as e x t e n d e d x - r a y a b s o r p t i o n fine
structure ( E X A F S ) a n d x - r a y a b s o r p t i o n n e a r e d g e
structure
(XANES)
spectroscopies
deliver
local
structural i n f o r m a t i o n [1]. W h i l e X A N E S is c o m p l i c a t e d t o interpret f r o m a structural point of v i e w , it
c o n t a i n s rather s i m p l e p h e n o m e n a like t h e c h e m i c a l
shift, w h i c h d e s c r i b e s t h e o x i d a t i o n state of t h e a t o m .
O n t h e o t h e r h a n d , E X A F S delivers a detailed picture
of t h e local e n v i r o n m e n t , a n d i n t e r a t o m i c s e p a r a t i o n s
c a n n o w a d a y s be d e t e r m i n e d with a n a c c u r a c y d o w n
to 100 f m [2]. In a d d i t i o n , E X A F S r e q u i r e s no periodic
s t r u c t u r e s (as r e q u i r e d in x-ray diffraction), a n d c a n
be readily a p p l i e d t o d i s o r d e r e d s y s t e m s , e.g., liquids.
L a s e r - p u m p S R - p r o b e e x p e r i m e n t s d e p e n d on the
available n u m b e r of X - r a y p h o t o n s per single pulse at
the repetition rate of t h e exciting laser, w h i c h is t y p i cally 1 k H z for c o m m e r c i a l a m p l i f i e d
fs-lasers.
T h e r e f o r e , s u c h e x p e r i m e n t s c a n u s e only a b o u t 10"
- 10" of the a v a i l a b l e p h o t o n flux at a s y n c h r o t r o n
with its m u c h h i g h e r p u l s e repetition rate of 100 5 0 0 M H z . W e h a v e p e r f o r m e d c a l c u l a t i o n s of t h e exp e c t e d p u m p - p r o b e signal for a g i v e n c o n d e n s e d
p h a s e c h e m i c a l s y s t e m [3,4], w h i c h a l s o u n d e r l i n e
the g e n e r a l utility of t i m e - r e s o l v e d X A S in c o n d e n s e d
phase dynamics research.
5
s p o n d s to t h e static (= u n e x c i t e d ) s a m p l e , w h i l e t h e
o t h e r X - r a y p u l s e s m o n i t o r the t r a n s m i s s i o n following
p h o t o e x c i t a t i o n at a n a d j u s t a b l e t i m e delay. T h e r e fore, the g a t e d integrator delivers a n o u t p u t of alternatively l a s e r - p u m p e d a n d u n p u m p e d intensities,
w h i c h are t h e n r e a d into t h e c o m p u t e r a n d a p p r o p r i ately s o r t e d . W i t h this s c h e m e w e c a n r e c o r d h i g h quality E X A F S s p e c t r a of the p h o t o i n d u c e d c h a n g e s .
I n d e e d , a careful a n a l y s i s of t h e m e a s u r e d noise
s h o w s that w e h a v e nearly a c h i e v e d t h e s h o t noise
limit in this c o n f i g u r a t i o n . T h e m e a s u r e d noise is c o n s i d e r a b l y r e d u c e d o v e r o t h e r m e t h o d s , w h i c h include
additional s y s t e m a t i c noise s o u r c e s . T h e s t e p - s c a n ning m o n o c h r o m a t o r i n d u c e s vibrations, w h i c h result
in a rather c o n s t a n t noise s o u r c e o n t h e t r a n s m i t t e d
intensity. T h i s is c o n s i d e r a b l y r e d u c e d , w h e n no o p tics m o v e , a n d t h e d e c r e a s i n g s t o r a g e ring c u r r e n t is
o b s e r v e d by a c o r r e s p o n d i n g b r o a d e n i n g of t h e pulse
height distribution. In a d d i t i o n , using our latest d e v e l o p m e n t by m e a s u r i n g the difference s p e c t r a during a
m o n o c h r o m a t o r s c a n r e d u c e s the noise e v e n m o r e .
After correcting t h e statistically d e r i v e d effective flux
for the limited X - r a y a b s o r p t i o n in the 30 urn thick
A P D , o u r m e a s u r e m e n t s are v e r y c l o s e t o t h e s p e c i fied flux of this b e a m l i n e [5].
6
EXPERIMENTAL APPROACH
T h e A L S camshaft mode c o n s i s t s of a c l o s e - p a c k e d
m u l t i b u n c h train f o l l o w e d by a 1 0 0 ns e m p t y s e c t i o n .
In this e m p t y s e c t i o n a ten-fold d e n s e r single e l e c t r o n
b u n c h is p l a c e d , w h o s e x - r a d i a t i o n ( d e t e c t e d with a n
A P D b e h i n d the s a m p l e ) w e single out with a g a t e d
integrator ( o p e n i n g w i n d o w c a . 2 0 ns). In o r d e r t o
r e c o r d high-quality s p e c t r a in a p u m p - p r o b e c o n f i g u ration w e h a v e e m p l o y e d the f o l l o w i n g s c h e m e : T h e
g a t e d integrator is t r i g g e r e d at t w i c e the laser repetition rate, so that e v e r y s e c o n d X - r a y p u l s e c o r r e -
RESULTS A N D DISCUSSION
W i t h o u r n e w difference-signal d e t e c t i o n s c h e m e w e
m a k e best u s e of the X - r a y s o u r c e , s i n c e the rec o r d e d noise o n t h e s e s p e c t r a c o r r e s p o n d nearly
entirely t o t h e e x p e c t e d s h o t n o i s e limit. But w e c a n
a l s o r e c o r d high-quality E X A F S w i t h o u t e m p l o y i n g
the difference m e a s u r e m e n t t e c h n i q u e . Fig. 1 illustrates this for the c a s e of a q u e o u s iodide. T h e e n e r g y
s p e c t r u m h a s a l r e a d y b e e n t r a n s f o r m e d into k-space
(Fig. 1a), but t h e original d a t a h a s not b e e n t r e a t e d
(e.g., s m o o t h e d or Fourier-filtered). T h i s s p e c t r u m
r e p r e s e n t s a single s c a n a c c u m u l a t i n g 2 5 0 0 single X ray p u l s e s per d a t a point. T h e fit ( a n d its Fourier
t r a n s f o r m , Fig. 1b) delivers a nice a g r e e m e n t with t h e
literature, a n d t h e a c c u r a c y for d e t e r m i n i n g t h e nearest n e i g h b o r shell of o x y g e n a t o m s is better t h a n
10 p m [4].
95
F i g . 1 : Static E X A F S a b o v e t h e L e d g e of iodine of a q u e o u s iodide ( N a l c o n c e n t r a t i o n : 0.7 mol/l, t h i c k n e s s :
0.1 m m ) . Original d a t a ( o p e n circles), a n d their fit (solid line) is s h o w n in a ) , a n d t h e Fourier t r a n s f o r m s h o w i n g t h e
n e a r e s t n e i g h b o r l-O d i s t a n c e in b) (solid line). For c o m p a r i s o n , a s i m u l a t i o n of t h e e x p e c t e d E X A F S of a t o m i c iodine is s h o w n ( d a s h e d c u r v e in a)) t o g e t h e r w i t h its Fourier t r a n s f o r m ( d a s h e d c u r v e in b)).
3
7100
7120
7140
7160
Fe'"(CN)
Te"(CN)
\
6
/
7200
static e x p .
6
\
7180
^
/
a
)
Fig. 1 a l s o illustrates t h e potential for m e a s u r i n g t h e
n e a r e s t - n e i g h b o r d i s t a n c e in p h o t o g e n e r a t e d i o d i n e
radicals. T h e l-O d i s t a n c e s h o u l d c h a n g e c o n s i d e r a bly u p o n p h o t o d e t a c h m e n t . V a l u e s for iodine a r e
c u r r e n t l y u n k n o w n , but in a t h e o r e t i c a l s t u d y of a q u e o u s Br radicals t h e p r e d i c t e d B r - 0 d i s t a n c e c h a n g e d
f r o m 3 3 5 p m for t h e ion to c a . 2 8 0 p m for t h e neutral
radical [6]. A s s u m i n g a similar r e d u c t i o n in t h e iodineo x y g e n d i s t a n c e s w o u l d result in a p r o n o u n c e d
c h a n g e in t h e E X A F S s i g n a l , a s s h o w n in t h e d a s h e d
c u r v e s in Fig. 1 .
Exploiting o u r d i f f e r e n c e m e a s u r e m e n t t e c h n i q u e w e
have attempted to measure the photoinduced chemical shift d u e to U V p h o t o i o n i z a t i o n of t h e c e n t r a l Fe
a t o m in a q u e o u s [ F e " ( C N ) ] " with a s y n c h r o n i z e d fs
laser. T h e c h e m i c a l shift of c a . 1 e V a r o u n d t h e Fe K
e d g e w a s o b s e r v e d in static s a m p l e s c o n t a i n i n g e i ther
[ F e " ( C N ) ] " or
[Fe"'(CN) ] "
(concentration
0.2 mol/l, s a m p l e t h i c k n e s s 0.1 m m ) , a s illustrated in
Fig. 2 a ) a n d b). T h e n w e e x c i t e d a liquid j e t with t h e
reactant s p e c i e s [ F e " ( C N ) ] " o n l y w i t h 100 jj,J of
2 6 6 n m light, a n d r e c o r d e d t h e t r a n s i e n t c h a n g e s .
D u e t o t h e low e x c i t a t i o n yield of b e l o w 0.4 % w e
c o u l d not o b s e r v e t h e c h e m i c a l shift o n t h e 100 ps
t i m e s c a l e (Fig. 2 c) a n d d)). H o w e v e r , w i t h i m p r o v e d
statistics e x p l o i t i n g t h e first 100 ns of t h e m u l t i b u n c h
train f o l l o w i n g p h o t o e x c i t a t i o n w e did o b s e r v e a
p h o t o i n d u c e d c h a n g e in t h e X A S . In Fig. 3 a ) , t h e
a v e r a g e of 2 0 s p e c t r a is s h o w n for e a c h , t h e u n p u m p e d a n d t h e p u m p e d s a m p l e (offset for clarity).
Fig. 3 b) s h o w s t h e d i f f e r e n c e signal of Fig. 3 a ) t o g e t h e r with a s i m u l a t i o n a s s u m i n g l a s e r - i n d u c e d
e v a p o r a t i o n of c a . 100 n m of t h e 0.1 m m thick s a m ple. W h i l e this nicely r e p r o d u c e s t h e majority of t h e
m e a s u r e d d i f f e r e n c e s p e c t r u m , w e still o b s e r v e s o m e
d i s c r e p a n c y a r o u n d t h e 1s -> 4 p pre e d g e f e a t u r e , a s
s h o w n in t h e residual s p o e c t r u m in Fig. 3 c). T h e
4
6
-v^N.
Laser on
At = 1 0 0 p s
6
• L a s e r off 1
f y s ^ y ^ '
7120
7140
7160
7180
Photon Energy / eV
6
6
-1.0 7100
4
7200
F i g . 2 : Static (a a n d b) a n d t i m e - r e s o l v e d X A S
(c a n d d) of a q u e o u s h e x a c y a n o f e r r a t e
samples
m e a s u r e d at b e a m l i n e 5 . 3 . 1 .
4
3
96
d o u b l e m i n i m u m s h a p e of d e c r e a s e d t r a n s m i s s i o n
(clearly visible in t h e s m o o t h e d s p e c t r u m ) indicates a
b r o a d e n i n g of this f e a t u r e , w h i c h h a s b e e n o b s e r v e d
in t e m p e r a t u r e - d e p e n d e n t
X A N E S studies.
The
e l e v a t e d t e m p e r a t u r e of the l a s e r - h e a t e d s a m p l e
c o u l d a c c o u n t for this o b s e r v a t i o n .
ACKNOWLEDGMENTS
W h i l e our c u r r e n t sensitivity d o e s not a l l o w t o u n a m b i g u o u s l y o b s e r v e t h e c h e m i c a l shift for less t h a n
0.4 % e x c i t e d s p e c i e s , c u r r e n t i m p r o v e m e n t s on t h e
laser e x c i t a t i o n p r o c e s s will permit us to b o o s t the
p r o d u c t yield into t h e 1-5 % r a n g e .
REFERENCES
7100
7100
7120
7120
7140
7140
7160
7160
7180
7180
T h i s w o r k w a s f i n a n c e d b y the F N R S via c o n t r a c t N o .
F N - 2 0 0 0 - 0 1 5 9 1 4 6 . 9 9 / 1 , b y t h e Swiss Light
Source,
the Advanced
Light Source, a n d by t h e U n i v e r s i t y of
Lausanne.
[1]
E.A. S t e r n , S . M . H e a l d , in: H a n d b o o k on S y n c h r o t r o n R a d i a t i o n , V o l . 1B, E d : E. E. K o c h ,
North H o l l a n d ( 1 9 8 3 ) , pp. 9 5 5 fff; B. K. A g a r w a l ,
X - R a y Spectroscopy, Springer (1991).
[2]
U. B u o n t e m p o ,
A. Filipponi,
P. P o s t o r i n o ,
R. Z a c c a r i , J . C h e m . P h y s . 108, 4 1 3 1 ( 1 9 9 8 ) .
[3]
C. Bressler, M. S a e s , M. C h e r g u i , P. P a t t i s o n ,
R. A b e l a , Nucl. I n s t r u m . M e t h . A 4 6 7 - 4 6 8 , 1444
(2001).
[4]
C. Bressler, M. S a e s , M. C h e r g u i , D. G r o l i m u n d ,
R. A b e l a , P. P a t t i s o n , J . C h e m . P h y s . 116, 2 9 5 4
(2002).
[5]
C. Bressler, M. S a e s , M. C h e r g u i , D. G r o l i m u n d ,
R. A b e l a , t o a p p e a r in: F e m t o c h e m i s t r y a n d
F e m t o b i o l o g y , e d . A. D o u h a l , W o r l d Scientific
(2002).
[6]
M. R o e s e l o v a , U. Kaldor, P. J u n g w i r t h , J . P h y s .
Chem.
A104,
6523
(2000).
7200
7200
X-Ray Probe Energy / eV
F i g . 3:
Time-resolved
XAS
(At = 100 n s )
(a),
difference s p e c t r u m t o g e t h e r with t r a n s i e n t s i m u l a t i o n
(b), a n d residue of the d a t a c o m p a r e d t o t h e
simulation.
97
UNCOMPENSATED SPINS IN ANTIFERROMAGNETIC NIO COUPLED TO A
FERROMAGNET
F. Nolting,
H. Ohldag
(LBNUSSRL),
E. Arenholz
J. Stöhr
(LBNL),
(SSRL)
A. Scholl
(LBNL),
A.T.
Young
(LBNL),
Hysteresis
loops of uncompensated
Ni spins in antiferromagnetic
NiO have been measured
absorption
spectroscopy
demonstrating
the sensitivity
of this technique.
The measurements
formed at an elliptically polarizing
undulator beamline at the Advanced
Light
Source.
INTRODUCTION
EXPERIMENT
T h e s a m p l e s t u d i e d w a s a multilayer of alternating
films of 3 n m C o a n d 50 n m N i O g r o w n o n S i . T h e
s u r f a c e ( C o on t o p ) w a s c a p p e d with a 1.5 n m Ru
layer to p r e v e n t its o x i d a t i o n . T h e e a s y axis of the C o
layer w a s in t h e p l a n e of the s a m p l e a n d a n e x c h a n g e
bias field of 1 7 5 O e w a s o b t a i n e d .
T h e X A S s p e c t r a w e r e d e t e r m i n e d by m e a s u r i n g the
s a m p l e current. T h e s a m p l e w a s m o u n t e d in g r a z i n g
i n c i d e n c e in t h e g a p of a n e l e c t r o m a g n e t , w h i c h c a n
s w i t c h a m a g n e t i c field u p to 3 0 0 0 O e with 1 H z a n d
h a s the m a g n e t i c field a l o n g t h e polarization v e c t o r of
the circularly p o l a r i z e d light. T h e h y s t e r e s i s l o o p s for
Ni as well a s for C o w e r e d e t e r m i n e d by v a r y i n g t h e
m a g n e t i c field f r o m - 3 0 0 0 O e t o + 3 0 0 0 O e a n d b a c k
in 50 O e s t e p s . A t e a c h m a g n e t i c field t h e a b s o r p t i o n
signal at t h e L a n d L e d g e for a fixed polarization is
m e a s u r e d . Next, the m e a s u r e m e n t is r e p e a t e d with
o p p o s i t e polarization. T h e hysteresis loop is c a l c u lated by t a k i n g the ratio of both polarizations for e a c h
e d g e a n d t h e n c a l c u l a t i n g the difference b e t w e e n L
a n d L loop.
2
3
2
0.6
0.4
'
I
.
Ni
;
M
V
\
\
X -04
-0.6
-0.8
-1.0
I
Jyiiiu a w j w
\\\
1
. . . . . . .
"nI
"FT
-3000
-2000
-1000
1000
2000
3000
1
1
1
1
1
1
15
10
^
5
^
n
CD
T h e investigation of m a g n e t i c multilayers is a n active
r e s e a r c h a r e a , d r i v e n by t h e interesting p h y s i c s a s s o ciated w i t h s u c h s t r u c t u r e s a n d their a p p l i c a t i o n in t h e
m a g n e t i c s t o r a g e industry. W h i l e the interface itself is
s u p p o s e d to d o m i n a t e t h e m a g n e t i c b e h a v i o r of t h e
entire s y s t e m , the identification a n d c h a r a c t e r i z a t i o n
of its m a g n e t i c p r o p e r t i e s r e m a i n s an e x p e r i m e n t a l
c h a l l e n g e . A p r o m i n e n t e x a m p l e is t h e s o - c a l l e d exc h a n g e bias effect, w h i c h is t h e directional c o u p l i n g
b e t w e e n t h e s p i n s in a n a n t i f e r r o m a g n e t a n d t h o s e in
an a d j a c e n t f e r r o m a g n e t , for a r e v i e w s e e [1]. A n i m portant p a r a m e t e r in m o d e l l i n g t h e e x c h a n g e b i a s
effect is t h e p o s s i b l e e x i s t e n c e of u n c o m p e n s a t e d
s p i n s in t h e a n t i f e r r o m a g n e t n e a r t h e interface. R e cently, w e d e m o n s t r a t e d t h e e x i s t e n c e of u n c o m p e n s a t e d Ni s p i n s in t h e C o / N i O s y s t e m with X M C D [2]
a n d P E E M [3] m e a s u r e m e n t s a n d related t h e m to an
o x i d a t i o n / r e d u c t i o n effect at t h e interface. H e r e w e
p r e s e n t h y s t e r e s i s l o o p s of e x c h a n g e b i a s e d C o / N i O
multilayer m e a s u r e d with X - r a y a b s o r p t i o n s p e c t r o s c o p y ( X A S ) . T h e e x p e r i m e n t w a s p e r f o r m e d at t h e
elliptically polarizing u n d u l a t o r b e a m l i n e 4 . 0 . 2 of t h e
A d v a n c e d Light S o u r c e , Berkeley, U S A .
3
I
1.0
0.8
with X-ray
were per-
s
-
\
o
\
1
1
5
-10
-15
20
C
v.
1
•
-3000
•
-2000
,
-100 0
0
I
1000
.
I
.
2000
I
3000
Applied Field (Oe)
F i g . 1 : H y s t e r e s i s loop for C o a n d Ni m e a s u r e d with
XAS.
T h e resulting l o o p s for C o a n d Ni are s h o w n in Fig. 1.
T h e data d e m o n s t r a t e s nicely that it is p o s s i b l e to
m e a s u r e t h e m a g n e t i c b e h a v i o u r of t h e small a m o u n t
of u n c o m p e n s a t e d Ni s p i n s at the C o / N i O interface.
Both l o o p s h a v e t h e s a m e c h a r a c t e r i s t i c s h o w i n g a
strong c o u p l i n g of t h e f e r r o m a g n e t i c C o m o m e n t s a n d
t h e u n c o m p e n s a t e d Ni s p i n s , a n d h e n c e c a n n o t explain the e x c h a n g e bias. Yet, w h e t h e r a small fraction
of t h e s e m o m e n t s is p i n n e d , that is t h e Ni h y s t e r e s i s
loop is not s a t u r a t e d in o n e direction, c a n n o t be excluded from these measurements.
ACKNOLEDGMENTS
S a m p l e s w e r e p r o d u c e d by Matt C a r e y at I B M , A l maden, USA.
REFERENCES
[1]
J . N o g u é s , I.K. Schuller, J . M a g n . M a g n . Mater.
192, 2 0 3 ( 1 9 9 9 ) .
[2]
F. N o l t i n g , E. A r e n h o l z , A . T . Y o u n g , A. S c h o l l ,
H. O h l d a g , J . Stöhr, A L S C o m p e n d i u m 2 0 0 0 ,
LBNL publication, 47838.
[3]
H. O h l d a g , T . J .
Regan,
J . Stöhr,
A. S c h o l l ,
F. Nolting,
J. Lüning,
C. S t a m m ,
S. A n d e r s ,
R. L. W h i t e , P h y s . Rev. Lett. 8 7 , 2 4 7 2 0 1 ( 2 0 0 1 ) .
98
PEEM MEASUREMENT OF MICROSTRUCTURED NIO THIN FILMS
F. Nolting,
L. Heyderman,
P.R.
Willmott
First results of domain patterns in NiO films grown on structured
substrates
are presented.
Si(001)
was
structured
with various shapes ranging in size from 150 nm to 8 pm and NiO was then deposited
using
pulsed reactive crossed-beam
laser
ablation.
INTRODUCTION
T h e c u r r e n t interest in m i c r o s t r u c t u r e d multilayers is
driven by their interesting p h y s i c s as well as by their
a p p l i c a t i o n in t h e m a g n e t i c - s t o r a g e industry. A p r o m i nent e x a m p l e is t h e s o - c a l l e d e x c h a n g e bias effect,
w h i c h is t h e directional c o u p l i n g b e t w e e n t h e s p i n s in
an a n t i f e r r o m a g n e t a n d t h o s e in a n a d j a c e n t ferrom a g n e t (For a r e v i e w s e e [1]). T h e d o m a i n s t r u c t u r e
of t h e a n t i f e r r o m a g n e t is e x p e c t e d to play a crucial
role a n d s t u d i e s h a v e b e e n m a d e to d e t e r m i n e t h e
effect of the m i c r o s t r u c t u r e o n t h e e x c h a n g e bias [2].
S o far, t h e s e m e a s u r e m e n t s w e r e either not spatially
r e s o l v e d or w e r e not able t o i m a g e the d o m a i n structure of t h e a n t i f e r r o m a g n e t directly. H e r e w e report o n
a first s t u d y t o m e a s u r e t h e d o m a i n s t r u c t u r e in a m i crostructured antiferromagnet.
esting i n f o r m a t i o n a b o u t t h e f o r m a t i o n of antiferromagnetic domains, an almost unexplored area.
EXPERIMENT
W e s t u d i e d a 4 0 n m NiO film g r o w n on s t r u c t u r e d
Si(001 ). T h e s t r u c t u r e s c o n s i s t e d of four different arrays: d o t s , rings, t r i a n g l e s a n d r e c t a n g l e s , r a n g i n g in
size f r o m 150 n m t o 8 urn. 100 n m high s t r u c t u r e s
w e r e p r o d u c e d in silicon by e l e c t r o n b e a m l i t h o g r a p h y
with C r lift-off f o l l o w e d by reactive ion e t c h i n g . A 3 n m
T i N buffer layer a n d 4 0 n m NiO film w e r e d e p o s i t e d
using p u l s e d reactive c r o s s e d - b e a m laser ablation [3]
on t h e Si s u b s t r a t e . P o w d e r X R D s u g g e s t e d heteroepitaxial g r o w t h .
S p e c t r o m i c r o s c o p i c m e a s u r e m e n t s w e r e p e r f o r m e d at
the A d v a n c e d Light S o u r c e , U S A , u s i n g t h e p h o t o e m i s s i o n e l e c t r o n m i c r o s c o p e ( P E E M ) at t h e b e n d i n g
m a g n e t b e a m l i n e 7.3.1.1 [4]. T u n i n g t h e p h o t o n e n ergy to the NiO L edge w e obtained the topographic
P E E M i m a g e s h o w n in Fig. 1a of a n a r e a with rings,
triangles a n d r e c t a n g u l a r s t r u c t u r e s . A n i m a g e of the
a n t i f e r r o m a g n e t i c structure, w h i c h w a s o b t a i n e d e m ploying t h e X M L D effect at the NiO L e d g e , is s h o w n
in Fig. 1b. A p p a r e n t l y , t h e d o m a i n s are s m a l l e r t h a n
the spatial resolution of the P E E M . A f e w bright a r e a s
in t h e overall d a r k i m a g e a p p e a r indicating a r e a s with
different a v e r a g e orientations of the a n t i f e r r o m a g n e t i c
axis. S p e c t r a r e c o r d e d in the bright a n d d a r k a r e a
(Fig. 1c) c o n f i r m the m a g n e t i c origin of t h e c o n t r a s t
difference. M o r e o v e r , t h e y s h o w the high quality of t h e
N i O films. T h e bright lines in t h e i m a g e are artefacts
of the i m a g e p r o c e s s i n g . T h e r e s e e m s to be no correlation b e t w e e n t h e t o p o g r a p h i c a n d a n t i f e r r o m a g netic structure.
Photon energy (eV)
F i g . 1 : a) T o p o g r a p h i c a n d b) m a g n e t i c P E E M i m a g e
of the N i O film, c) Local s p e c t r a r e c o r d e d in t h e bright
a n d dark a r e a .
3
2
In t h e f u t u r e , w e will o p t i m i s e t h e s a m p l e s t o f u r t h e r
e x p l o r e the influence of t h e m i c r o s t r u c t u r e o n the exc h a n g e bias. T h e s e s t u d i e s c o u l d a l s o deliver inter-
ACKNOWLEDGMENTS
S u p p o r t at t h e P E E M f r o m A. S c h o l l , A L S , is gratefully
acknowledged.
REFERENCES
[1]
J . N o g u é s , I.K. Schuller, J . M a g n . M a g n . Mater.
192, 2 0 3 ( 1 9 9 9 ) .
[2]
A. M o u g i n et al. A p p l . P h y s . 8 9 , 6 6 0 6 ( 2 0 0 1 ) .
[3]
P.R. W i l l m o t t , J.R. Huber, Rev. M o d . P h y s . 7 2 ,
315(2000).
[4]
S. A n d e r s et al.,
(1999).
Rev.
Sei.
Instrum.
70,
3973
99
HIGH RESOLUTION TESTS OF THE SLS POWDER DIFFRACTOMETER
F. Gozzo,
Th. Bortolamedi,
M. Lange,
D. Maden,
J. Rothe,
B. Schmitt,
J. Welte,
B.D.
Patterson
Standard
Si and LaB powders
and a Si(111) single crystal were used to test the resolution
of the multicrystal analyser detection system of the powder diffractometer
on the SLS Materials Science Beamline.
A
20linewidth
of better than 0.005° with the single crystal and better than 0.01° with the LaB powder
were
measured.
6
6
INTRODUCTION
T h e p o w d e r d i f f r a c t o m e t e r at t h e S L S M a t e r i a l s S c i ence (MS) beamline has two independent detection
s y s t e m s : a multicrystal a n a l y s e r detector, for high
a n g u l a r resolution (better t h a n 0.005°), a n d a w i d e a n g l e , Si microstrip d e t e c t o r for h i g h - s p e e d (sub-millis e c o n d ) d a t a acquisition at a n g u l a r resolution better
t h a n 0.02°. W e report here o n t h e h i g h - r e s o l u t i o n
m o d e of o p e r a t i o n . Details o n t h e microstrip d e t e c t o r
are f o u n d in a s e p a r a t e c o n t r i b u t i o n by B. S c h m i t t et
al. [1].
Optics tuning and resolution tests were performed
using t w o s t a n d a r d p o w d e r s f r o m t h e U.S. N a t i o n a l
Institute of S t a n d a r d s a n d T e c h n o l o g y ( N I S T ) (Si 6 4 0 c
a n d L a B 6 6 0 a ) a n d a S i ( 1 1 1 ) single crystal.
6
MULTICRYSTAL ANALYSER-DETECTOR
T h e S L S multicrystal a n a l y s e r detector is b a s e d on a
d e s i g n by H o d e a u et al [2]. Five S i ( 1 1 1 ) crystals are
m o u n t e d o n a H u b e r d o u b l e g o n i o m e t e r with a 2°
intercrystal offset in 29. T h e s e c o n d a x i s of the d o u b l e
g o n i o m e t e r m o v e s a s y s t e m of five scintillator-photomultiplier d e t e c t o r s as a unit. It is s u p p l i e d by
S C I O N I X ( N e t h e r l a n d s ) a n d c o n s i s t s N a l ( T I ) scintillator crystals ( 0 2 0 m m , 2 m m thick) optically c o u p l e d t o
H a m a m a t s u R 1 9 2 4 p h o t o m u l t i p l i e r s , e a c h of w h i c h is
f o l l o w e d by a p r e a m p l i f i e r ( g a i n : 30 m V / k e V with
50 O h m t e r m i n a t i o n ) . Fig. 1 s h o w s a d r a w i n g of t h e
a n a l y z e r - d e t e c t o r set up.
Scintillators/photomultipliers
offset a l l o w s t h e o p e r a t o r t o satisfy t h e B r a g g c o n d i tion at a g i v e n i n c o m i n g p h o t o n e n e r g y for all t h e five
c h a n n e l s t o g e t h e r , by s i m p l y rotating t h e d o u b l e g o n i o m e t e r in a 2:1 ratio. During t h e a c q u i s i t i o n of a 26
s c a n , t h e five a n a l y s e r d e t e c t o r c h a n n e l s intercept
diffraction p e a k s o n e after the other, yielding indep e n d e n t 26 s c a n s . T h e statistics are t h u s i n c r e a s e d by
a f a c t o r of five w i t h o u t i n c r e a s i n g t h e d a t a acquisition
t i m e , with t h e o n l y r e q u i r e m e n t of m e r g i n g t h e data at
t h e e n d of t h e m e a s u r e m e n t .
T h e five S i ( 1 1 1 ) crystals h a v e to b e carefully m o u n t e d
o n t h e d o u b l e g o n i o m e t e r a n d their a n g u l a r offset
m a n u a l l y a d j u s t e d t o be v e r y c l o s e t o t h e n o m i n a l 2°
value. Although the data merging process can accept
arbitrary offsets, the m o u n t i n g m u s t be precise for t h e
following reasons:
• t h e relative positions of the crystals on t h e
g o n i o m e t e r plate h a v e b e e n c h o s e n to m i n i m i z e
beam shadowing.
• for e a c h p h o t o n e n e r g y , t h e r e exists an o p t i m u m
c r y s t a l - t o - d e t e c t o r d i s t a n c e , for w h i c h the diffracted
b e a m s hit t h e c e n t e r of e a c h scintillator, but o n l y if
t h e s y s t e m of five crystals is s y m m e t r i c with
r e s p e c t t o t h e central crystal.
T h e o p t i m u m d i s t a n c e , as a f u n c t i o n of t h e p h o t o n
e n e r g y , is o b t a i n e d by translating the scintillators
a l o n g a t r a n s l a t i o n s t a g e , a s s h o w n in Fig. 1. Fig. 2
s h o w s t h e result of a g r a p h i c a l d e t e r m i n a t i o n of the
o p t i m u m c r y s t a l - t o - d e t e c t o r d i s t a n c e as a f u n c t i o n of
e n e r g y , t o g e t h e r with a fit t o an e x p o n e n t i a l f u n c t i o n .
; S i ( l l l ) crystal-to-detector optimum distance
Si(111) crystals
© Calculated points with AUTOCAD
™™»fitwith an ExpDecay3 function
He c h a m b e r
translation
stage
5000 10000 15000 20000 25000 30000 35000 40000 45000
E n e r g y [eV]
Fig. 1 : The SLS five-channel analyser-detector
up.
set
E a c h a n a l y s e r crystal c o r r e s p o n d s t o a particular d e tector c h a n n e l . M o u n t i n g t h e crystals at an a n g u l a r
Fig. 2: The optimum, energy-dependent,
detector d i s t a n c e .
crystal-to-
100
RESOLUTION TESTS
V e r y h i g h - r e s o l u t i o n s t u d i e s , s u c h a s crystallographic
investigations or m i c r o s t r u c t u r e d e t e r m i n a t i o n s , require b o t h high e n e r g y resolution a n d high a n g u l a r
resolution, since b o t h c o n t r i b u t i o n s directly influence
the diffraction p e a k line s h a p e .
T h e M S b e a m l i n e o p t i c s is d e s c r i b e d in a s e p a r a t e
contribution by P a t t e r s o n et al. [3]. It c o n s i s t s of a
d o u b l e crystal m o n o c h r o m a t o r , p r e c e d e d by a cylindrical mirror, w h i c h c o l l i m a t e s t h e incident radiation in
the vertical direction, f o l l o w e d by a s e c o n d cylindrical
mirror, w h i c h f o c u s e s t h e b e a m at t h e s a m p l e position. T h e e n e r g y resolution (AX/X < 2 x 1 0 " ) d e p e n d s ,
therefore, o n t h e quality a n d c u r v a t u r e of the first mirror. T h e a n g u l a r resolution, on t h e other h a n d , d e p e n d s o n t h e residual vertical a n d horizontal diverg e n c e at the s a m p l e position a n d t h e intrinsic a n a lyser/detector a n g u l a r resolution. T h e latter d e p e n d s
on the S i ( 1 1 1 ) crystal quality (rocking curve w i d t h ) a n d
the p r e s e n c e of s t r e s s a n d c u r v a t u r e i n d u c e d d u r i n g
the m o u n t i n g of the crystals o n t o their m e c h a n i c a l
s u p p o r t s . T h e Si ( 1 1 1 ) crystals w e r e p r e - c h a r a c t e r i z e d
using a Seifert X R D 3 0 0 3 P T S - H R diffractometer at
PSI a n d c h e c k e d a g a i n s t i n d u c e d c u r v a t u r e a n d
s t r e s s using different g l u e s . R o c k i n g c u r v e w i d t h s
better t h a n 0 . 0 0 2 ° w e r e m e a s u r e d w i t h C u K radiation, a n d t h e effects of c u r v a t u r e a l o n g t h e entire
crystal s u r f a c e w e r e f o u n d to be b e l o w 0 . 0 0 5 ° , w h e n
using E p o t e c n y E 7 0 7 .
a parallel b e a m at t h e s a m p l e position ( s e c o n d mirror
flat).
T h e s a m e crystal w a s u s e d to test the overall r e s o l u tion with t h e m u l t i - a n a l y s e r detector. Fig. 4 s h o w s oo20 s c a n s of the ( 1 1 1 ) reflection at 1 2 k e V . U s i n g t h e
f r o n t - e n d slits, w e r e d u c e d t h e 0.23 m r a d b e a m diverg e n c e by f a c t o r s of 30 a n d 8 0 , resulting in m e a s u r e d
F W H M linewidths of 0 . 0 0 4 7 ° a n d 0 . 0 0 2 5 ° in 29. T h e
s h a r p e s t linewidth r e p r o d u c e s , within t h e a c c u r a c y of
t h e rotation s t a g e s (±2 a r c s e c ) , t h e e x p e c t e d r o c k i n g
c u r v e w i d t h for Si(111 ) at this e n e r g y .
4
a
Fig. 3 s h o w s t h e effect of mirror c u r v a t u r e on t h e e n e r g y a n d a n g u l a r resolution.
&
300000
>>
nrei
200000
100000
-18.94 -18.93 -18.92 -18.91 -18.90 -18.89 -18.88 -18.87 -18.86
40000
(111)
ÎT
30000
*««
20000
S
10000
s
-2*
0.0025°
•
1
-18.94 -18.93 -18.92 -18.91 -18.90 -18.89 -18.88 -18.87 -18.86
2 e(deg)
F i g . 4 : Si ( 1 1 1 ) co-20 s c a n s using t h e multi-crystal
a n a l y s e r d e t e c t o r with 7.7 (top) a n d 2.9 ( b o t t o m ) m i croradian beam divergence.
R e s o l u t i o n t e s t s with p o w d e r s w e r e p e r f o r m e d using
t h e t w o n e w s t a n d a r d p r o d u c t s f r o m N I S T : t h e Si 6 4 0 c
a n d L a B 6 6 0 a p o w d e r s . W i t h t h e Si p o w d e r , w e w e r e
not able t o m e a s u r e (111) linewidths s m a l l e r t h a n
a p p r o x i m a t e l y 0 . 0 1 3 ° at 12 k e V p h o t o n e n e r g y . W e
interpret this v a l u e a s t h e intrinsic p e a k w i d t h , s i n c e it
r e m a i n e d u n c h a n g e d after t u n i n g t h e b e a m l i n e optics.
6
U s i n g the n e w s t r e s s - f r e e L a B 6 6 0 a N I S T s t a n d a r d
p o w d e r , w e w e r e a b l e t o m e a s u r e at 12 k e V
linewidths b e l o w 0.01° with fairly r e l a x e d o p t i c s ( b e a m
d i v e r g e n c e r e d u c e d only by a factor of 5 a n d f o c u s e d
b e a m ) - s e e Fig. 5. H o w e v e r , w e w e r e o n c e a g a i n
limited by t h e intrinsic p o w d e r linewidth, since flattening t h e s e c o n d mirror t o collimate the b e a m at t h e
s a m p l e position p r o d u c e d only a d e c r e a s e in flux
w i t h o u t a n y r e d u c t i o n in linewidth.
6
<o (deg)
F i g . 3: Effect of mirror c u r v a t u r e o n e n e r g y a n d a n g u lar resolution.
T h e effects on t h e r o c k i n g curve w i d t h of the singlecrystal Si (333) B r a g g reflection w e r e o b s e r v e d using
a w i d e - a c c e p t a n c e Si p h o t o d i o d e as detector. T h e
crystal w a s m o u n t e d o n a H u b e r Eulerian cradle in
d i s p e r s i v e c o n f i g u r a t i o n , at t h e s a m p l e position of the
diffractometer, in o r d e r to be sensitive t o t h e incident
beam divergence. The smaller energy and angular
s p r e a d s c o r r e s p o n d , a s e x p e c t e d , to a c o l l i m a t e d
vertical b e a m o n the first crystal (first mirror bent) a n d
U s i n g t h e L a B s a m p l e , w e s t u d i e d t h e d e p e n d e n c e of
t h e linewidth o n 20.
6
T h i s d e p e n d e n c e is k n o w n a s t h e Instrumental R e s o lution F u n c t i o n (IRF), for w h i c h S a b i n e has determ i n e d analytical e x p r e s s i o n s in for multi-crystal s p e c t r o m e t e r s a n d parallel b e a m optics [4]. Fig. 6 s h o w s
t h e e x p e r i m e n t a l IRF d e t e r m i n e d at 1 2 k e V , with a
vertically-focused b e a m .
101
REFERENCES
-40.20
-40.18 -40.16
-40.14
-40.12
-40.10 -40.08
2 G (deg)
F i g . 5: Diffraction intensity f r o m t h e ( 3 0 0 ) reflection of
the s t a n d a r d N I S T L a B p o w d e r .
[1]
B. S c h m i t t ,
Ch. Brönnimann,
E.F. E i k e n b e r r y ,
M. Naef, F. G o z z o , B.D. P a t t e r s o n , R. Horisberger, Status of the MYTHEN Detector System, PSI
Scientific R e p o r t 2 0 0 1 , V o l u m e V I I .
[2]
J.L. H o d e a u ,
P. Bordet,
M. A n n e ,
A. Prat,
A . N . Fitch, E. D o o r y h e e , G . V a u g h a n , A. F r e u n d ,
Nine
Crystal
Multi-analyser
Stage
for
High
Resolution
Powder Diffraction
between 6 and 40
keV, Proc. S P I E 3 4 4 8 ( 1 9 9 8 ) , 3 5 3 .
[3]
B.D. P a t t e r s o n et. al., The SLS Materials
Science
Beamline,
PSI Scientific R e p o r t 2 0 0 1 , V o l u m e
VII.
[4]
T . M . S a b i n e , J . A p p l . Cryst. 2 0 ( 1 9 8 7 ) , 173.
6
ACKNOWLEDGEMENT
60
We
thank
H. G r i m m e r ,
D. G r u e t z m a c h e r
and
D. C l e m e n s for their c o m p e t e n t h e l p at t h e PSI Seifert
d i f f r a c t o m e t e r a n d S. C o c k e r t o n , Crystal Scientific, for
his v a l u a b l e s u g g e s t i o n s on strain-free m o u n t i n g of
single crystals.
LaB 660a M S T stau dard powd er
•
0
À
\
6—
20
40
•*
w
60
80
2 e (deg)
F i g . 6: E x p e r i m e n t a l i n s t r u m e n t a l resolution f u n c t i o n
m e a s u r e d at 12 k e V .
PLANS FOR THE FUTURE
W e plan to p e r f o r m t h e f o l l o w i n g m e a s u r e m e n t s :
•
A s y s t e m a t i c s t u d y of t h e
Instrumental
R e s o l u t i o n F u n c t i o n for different e n e r g i e s a n d
a s a f u n c t i o n of different optics p a r a m e t e r s ,
using a s t a n d a r d r e f e r e n c e s a m p l e with s m a l l
intrinsic linewidth.
•
A s t u d y of the size a n d s h a p e of the b e a m
s p o t at the s a m p l e position for different optics
parameters.
102
RESIDUAL STRESS ANALYSIS IN CUBIC LPPS ZIRCONIA COATINGS USING
SYNCHROTRON RADIATION X-RAY DIFFRACTION (XRD)
Th. Bortolamedi,
We studied
residual
lised)
zirconia
flects
the presence
direction
normal
stress
at 8.1 and
M. Lange, D. Maden, B. Schmitt, B.D. Patterson,
M. Loch, G. Barbezat (Sulzer Metco,
Wohlen)
fields
in Low Pressure
13.2 keV.
of residual
stress
to the coating
Plasma
For both energies,
gradients
and/or
Sprayed
(LPPS)
sin y/plots
show
2
a variation
F.
coatings
Gozzo
of cubic
a non-linear
of in-plane
mechanical
which
properties
re-
in the
surface.
INTRODUCTION
g r a p h y d i r e c t i o n . For (hkl) p l a n e s parallel t o t h e sur-
K n o w i n g the residual s t r e s s field in c o a t e d c o m p o n e n t s is a p r i m a r y r e q u i r e m e n t for their c o r r e c t d e s i g n
a n d p r o d u c t i o n . A d h e s i o n , for i n s t a n c e , s t r o n g l y d e p e n d s o n t h e residual s t r e s s a n d , in particular, o n the
residual s t r e s s m i s m a t c h b e t w e e n c o a t i n g a n d s u b s t r a t e . T h e u s e of S y n c h r o t r o n R a d i a t i o n ( S R ) X R D is
particular useful t o p r o b e c o a t i n g s a n d t h i n f i l m s at
different p e n e t r a t i o n d e p t h s . X R D p r o v i d e s a n o n d e s t r u c t i v e t e c h n i q u e for i n v e s t i g a t i n g t h e strain distribution in c o a t e d c o m p o n e n t s , f r o m w h i c h t h e s t r e s s
distribution c a n be o b t a i n e d using a s u i t a b l e m e c h a n i cal m o d e l l i n g [1]. T h e r e a r e m a n y b e n e f i t s of using
s y n c h r o t r o n radiation i n s t e a d of a c o n v e n t i o n a l X - r a y
t u b e . T h e y a r e a s s o c i a t e d w i t h t h e high brilliance, t h a t
drastically r e d u c e s t h e m e a s u r e m e n t t i m e , the v a r i able w a v e l e n g t h a n d m o n o c h r o m a t i c i t y , a n d highly
parallel (line or point) b e a m .
f a c e , \j/=0. T h e
information
d e p t h tells u s h o w
a n g l e 6, t h e \\i tilting a n g l e a n d the p h o t o n
through the
linear a b s o r p t i o n
It s h o u l d ,
t h e r e f o r e , be c o m p a r e d with t h e s u r f a c e
roughness
(1.29 u,m in o u r s a m p l e s ) a n d the overall f i l m thickn e s s , a n d t a k e n into a c c o u n t
in t h e c h o i c e of the
w o r k i n g p h o t o n e n e r g y . Fig. 1 s h o w s t h e i n f o r m a t i o n
d e p t h a s a f u n c t i o n of the \\i tilting a n g l e , c a l c u l a t e d for
several photon energies.
16KeV
— -
-
—
«. _
—
;
•—
12KeV
- lOKeV
—•8.1 KeV
— 7KeV
«S.
«S.
"x
R e c e n t a d v a n c e s in P l a s m a S p r a y t e c h n o l o g y h a v e
led t o i m p r o v e d p r o c e s s c o n t r o l , a l l o w i n g the d e p o s i tion of v e r y t h i n , d e n s e a n d h o m o g e n e o u s c e r a m i c
layers [2]. T h e c o a t i n g t h i c k n e s s usually r a n g e s f r o m
t e n s of m i c r o n s t o s e v e r a l m i l l i m e t e r s , d e p e n d i n g o n
the s p e c i f i c u s e .
T h e c o a t i n g t e s t e d is 2 0 % Yttria-stabilised Z i r c o n i a
( Y - S Z ) with a t h i c k n e s s of a b o u t 2 0 u,m o n a s t a i n l e s s
steel X 5 C r N i 1 8 - 1 0 s u b s t r a t e , grit b l a s t e d w i t h a l u m i n u m o x i d e b e a d s ( d i a m e t e r r a n g e 1 5 0 - 4 2 5 u,m) to
i m p r o v e the c o a t i n g ' s a d h e s i o n . T h e m a i n L P P S f e a t u r e s a r e high d e n s i t y (6 g / c m ) a n d low p o r o s i t y (less
t h a n 2 % ) . F u r t h e r m o r e , the L P P S t e c h n i q u e , in c o m p a r i s o n with P V D a n d C V D [3] l e a d s t o i n - p l a n e s t r e s s
fields,
which
frequently
are
equibiaxial
(e.g.
<*ii= O 2 2 . <*33= o¡j=0 w i t h i * j ) , b e c a u s e , d u r i n g c o o l i n g ,
the p l a s m a d r o p l e t s c o n t r a c t or e x p a n d a l o n g a p l a n a r
d i r e c t i o n . T h e s e c o a t i n g s w e r e d e p o s i t e d by S u l z e r
M e t c o in t h e f r a m e w o r k of a j o i n t S L S - S u l z e r M e t c o
r e s e a r c h project.
2
W h e n i n v e s t i g a t i n g residual s t r e s s g r a d i e n t s , a n i m portant p a r a m e t e r t o c o n s i d e r is the a v e r a g e i n f o r m a where
energy,
coefficient.
Plasma spray and sample parameters
e_ sinflcosy
the
d e p t h of a n a l y s i s c h a n g e s a s a f u n c t i o n of t h e B r a g g
EXPERIMENTAL SETUP
tion d e p t h , d e f i n e d a s
(Yttria-stabi-
behavior,
u, is t h e
linear a b s o r p t i o n coefficient a n d \\i is t h e tilting a n g l e
[4]. \\i is d e f i n e d a s the a n g l e b e t w e e n t h e n o r m a l to
the s u r f a c e a n d t h e n o r m a l to t h e s e l e c t e d crystallo-
• x
•
.
0
o
i
.
10"
;
20"
.
.
30°
;
40°
.
i
50"
.
n \
1 "TW*
•
60"
X
70"
80°
90°
Tilting angle (y)
F i g . 1 : Y - S Z I n f o r m a t i o n d e p t h v e r s u s \j/ tilting a n g l e s ,
f o r different p h o t o n e n e r g i e s .
T h e sin yr
2
method and experiment
The most popular experimental X R D approach to the
e v a l u a t i o n of residual s t r e s s e s in polycrystalline m a t e rials is t h e sin \j/
2
method.
For e a c h s e l e c t e d
(hkl)
c r y s t a l l o g r a p h i c d i r e c t i o n , diffraction d a t a a r e c o l l e c t e d
at different \j/ tilting a n g l e s . T h e m e t h o d r e q u i r e s a 6 26 s c a n f o r e v e r y y a n g l e a r o u n d t h e s e l e c t e d diffraction p e a k a n d , in o r d e r to e m p h a s i z e t h e p e a k shifts, it
is i m p o r t a n t to w o r k at t h e h i g h e s t p o s s i b l e 26 a n g l e .
T h e e x p e r i m e n t s w e r e p e r f o r m e d using t h e h i g h r e s o l u t i o n d e t e c t o r s y s t e m of t h e p o w d e r d i f f r a c t o m e ter
at
the
SLS
Materials
Science
Beamline.
T w o p h o t o n e n e r g i e s w e r e c h o s e n , 8.1 a n d 13.2 e V ,
t o i n v e s t i g a t e different p e n e t r a t i o n d e p t h s . 8.1 e V
( c o r r e s p o n d i n g t o t h e C u Koc radiation) w a s c h o s e n to
have a comparison with m e a s u r e m e n t s performed
w i t h t h e PSI Seifert® diffractometer, a n d 13.2 e V a s
the highest energy ( m a x i m u m penetration depth) be-
103
fore exciting a s t r o n g a b s o r p t i o n e d g e , w h i c h w o u l d
have produced a severe fluorescence background.
p r o p e r t i e s ) c o n c e r n s , t h e r e f o r e , c o n c e r n i n g m o s t l y the
first layers b e l o w t h e c o a t i n g s u r f a c e .
W e note that t h e c h o i c e of the c r y s t a l l o g r a p h i c direction t o s t u d y t h e residual s t r e s s , f o l l o w e d , in this c a s e ,
an additional criterion with r e s p e c t t o the o n e des c r i b e d a b o v e (high 29 v a l u e for high sensitivity t o
shifts). In fact, this c o a t i n g is not a perfect isotropic
m a t e r i a l , a n d t h e r e f o r e t h e (331) c r y s t a l l o g r a p h i c direction is a g o o d c o m p r o m i s e b e t w e e n high stiffness
( H = 0 ) a n d high c o m p l i a n c e ( H = 1 ) directions. U s i n g
the K r ö n e r m o d e l [5], w e h a v e :
W e a l s o note that no splitting w a s o b s e r v e d in t h e
sin \j/ plots for positive a n d n e g a t i v e \\t tilting a n g l e s ,
indicating t h e a b s e n c e of s h e a r s t r e s s c o m p o n e n t s .
2
2
2 2
3x(h k
—
2
2 2
+ hl + kl)
Ö
2
ï
2
T~i
2 2
(h +k +l )
H(33i) 0 . 8 1 .
=
RESULTS A N D DISCUSSION
P r e l i m i n a r y t e x t u r e m e a s u r e m e n t s p e r f o r m e d using
the PSI Seifert® diffractometer d e m o n s t r a t e d t h e a b s e n c e of t e x t u r e in t h e films.
Figure 2 s h o w s t h e (331 ) diffraction intensity at different \j/ a n g l e s a n d 13.2 k e V . T h e o b s e r v e d p e a k shift
indicates the p r e s e n c e of residual s t r e s s . E q u i v a l e n t
data w e r e c o l l e c t e d at 8.1 k e V .
0.0
0.2
0.6
0.4
Sin
0.8
Ï.0
~\y
F i g . 3: Sin \j/ plot for Y - S Z c o a t i n g m e a s u r e d by S R
X R D at t w o e n e r g i e s a l o n g t h e (331 ) c r y s t a l l o g r a p h i c
direction.
2
A d d i t i o n a l investigations a n d data a n a l y s i s are b e i n g
p e r f o r m e d in o r d e r t o better u n d e r s t a n d t h e origin of
t h e o b s e r v e d effects.
REFERENCES
46.6°
46.8°
47.0°
47.2°
47.4°
47.6°
47.8°
48.0°
48.2°
Angle (26)
F i g . 2 : P e a k shift with \j/ tilting in Y - S Z d u e to p r e s e n c e of the in-plane residual s t r e s s .
Fig. 3 s h o w s t h e sin \j/ plots o b t a i n e d f r o m t h e (331 )
B r a g g reflection at 8.1 a n d 13.2 k e V . T h e plots s h o w a
c u r v a t u r e in t h e sin \j/ t r e n d for high \j/ tilting a n g l e s .
T h i s b e h a v i o r c o u l d be e x p l a i n e d by t h e p r e s e n c e of
residual s t r e s s g r a d i e n t s ( i n c r e a s i n g c o m p r e s s i o n
b e l o w t h e c o a t i n g t o p s u r f a c e ) a n d / o r a variation of
the in-plane m e c h a n i c a l p r o p e r t i e s with d e p t h . T h e
higher d e g r e e of c u r v a t u r e o b s e r v e d at 8.1 k e V c a n
be e x p l a i n e d in t e r m s of lower a v e r a g e p e n e t r a t i o n
d e p t h at l o w e r p h o t o n e n e r g i e s . T h e o b s e r v e d effect
(stress g r a d i e n t or variation of in-plane m e c h a n i c a l
[1]
I.C. N o y a n , J . B . C o h e n , R e s i d u a l s t r e s s - M e a s urement
by
diffraction
and
interpretation,
S P R I N G E R - V E R L A G , 1987.
[2]
M. L o c h , G. B a r b e z a t , Spraying thin coating
very
quickly,
S U L Z E R T E C H N I C A L R E V I E W 2/99,
1999 pp.12-15. www.sulzermetco.com/
[3]
P. S c a r d i ,
M. L e o n i ,
Y.H Dong,
Texture
determination
in highly stressed PVD films, A D V .
X ray A N A L . , 4 2 ( 1 9 9 9 ) p p . 4 9 2 - 5 0 1 .
[4]
C. G e n z e l ,
Conference
2001).
[5]
V. H a u k , Structural a n d residual s t r e s s a n a l y s i s
by n o n d e s t r u c t i v e m e t h o d s - E v a l u a t i o n a p p l i c a tion a s s e s s m e n t , E L S E V I E R A m s t e r d a m ( 1 9 9 7 ) .
2
2
Proceedings
pp.33-34,
of the Size-Strain
Trento (December
III
2-5,
ACKNOWLEDGEMENT
W e t h a n k H. G r i m m e r for his c o m p e t e n t help at t h e
PSI Seifert diffractometer. W e a l s o t h a n k P. S c a r d i for
his v a l u a b l e s u g g e s t i o n s a n d d i s c u s s i o n s during
c o u r s e of this w o r k .
104
NOVEL MATERIALS GROWN WITH PULSED LASER ABLATION EPITAXY
P.R. Willmott,
B.D. Patterson,
D.
Rossetti
Pulsed reactive crossed beam laser ablation (PRCLA) has been used to synthesize
novel hard
materials
and structures.
In addition, a new in-situ growth chamber based on PRCLA and pulsed laser
deposition
has been designed for use in conjunction
with a five-circle diffractometer
in the surface diffraction
station
of the Materials Science Beamline.
The chamber has the largest reported Be-window
for access to a large
region of reciprocal
space, while maintaining
flexibility and in-situ processing
capabilities.
INTRODUCTION
a n d low coefficient of friction (C = Z r C N i _ ) , r e s p e c tively. T h e m u l t i l a y e r s t r u c t u r e c o u l d be s i m p l y realised b y u s i n g a m u l t i p l e - c o m p o n e n t a b l a t i o n rod of
ZrA//Ti a n d m e t h a n e / n i t r o g e n g a s m i x t u r e s . T h e h a r d n e s s of t h e s e s t r u c t u r e s s h o w e d a n i m p r o v e d h a r d n e s s c o m p a r e d to bilayer s t r u c t u r e s ( A B ) of a p p r o x i m a t e l y 1 5 % . E x p e r i m e n t s are p l a n n e d to f u r t h e r
i n c r e a s e their h a r d n e s s (see Fig. 2 ) .
x
A n i m p o r t a n t c h a l l e n g e in m o d e r n c o n d e n s e d m a t t e r
p h y s i c s is t h e d i s c o v e r y a n d c h a r a c t e r i z a t i o n of n o v e l
t e c h n o l o g i c a l m a t e r i a l s [1]. M a n y of t h e s e m a t e r i a l s
h a v e c o m p l i c a t e d s t o i c h i o m e t r i e s a n d crystal struct u r e s t h a t w o u l d be i m p o s s i b l e t o g r o w u s i n g e s t a b lished t h e r m a l t e c h n i q u e s . T e c h n i q u e s t h a t c a n g r o w
films f a r f r o m t h e r m a l e q u i l i b r i u m m a y b e c a p a b l e of
p r o d u c i n g n o n t h e r m a l s t a t e s i n a c c e s s i b l e to t h e r m a l
routes. P u l s e d laser d e p o s i t i o n ( P L D ) is s u c h a t e c h nique [2]. A n a d a p t a t i o n of P L D in w h i c h the a d d i t i o n
of a g a s pulse p r o v i d e s i m p o r t a n t f u n d a m e n t a l a n d
t e c h n o l o g i c a l benefits has b e e n d e v e l o p e d at t h e U n i v e r s i t y of Z u r i c h (see Fig. 1 ).
x
n
ablation target
F i g . 2 : A c o m p a r i s o n of h a r d n e s s of s i n g l e layer Z r N
a n d ZrCo.6N .4 a n d m u l t i l a y e r f i l m s . T h e w h i t e b a r s
c o r r e s p o n d t o t h e p u r e nitrides ( x = 0 ) , w h i l e the b l a c k
bars are for c a r b o n i t r i d e films with x = 0 . 6 .
0
F i g . 1 : T h e principle of p u l s e d reactive c r o s s e d - b e a m
laser a b l a t i o n .
T h e t e c h n i q u e is c a l l e d p u l s e d reactive c r o s s e d - b e a m
laser a b l a t i o n ( P R C L A ) a n d h a s b e e n d e m o n s t r a t e d
for a w i d e r a n g e of t e c h n o l o g i c a l m a t e r i a l s . S o m e
e x a m p l e s are n o w g i v e n .
LABORATORY EXPERIMENTS
Novel superhard multilayer structures have been
g r o w n u s i n g P R C L A , b a s e d o n transition m e t a l c a r b o nitrides [3,4]. T h e s t r u c t u r e s h a v e a n ( A B A C ) fourlayer
periodicity,
where
every
second
layer
(A = V C N i _ ) is a n ultrathin layer of softer m a t e r i a l ,
w h i c h i m p r o v e s t h e e f f i c i e n c y of t e r m i n a t i o n of m i c r o crack propagation.
T h e o t h e r m a t e r i a l s , B a n d C,
w e r e c h o s e n for their h i g h h a r d n e s s (B = T i C x N ^ )
n
x
x
T h e s e c o n d e x a m p l e is t h e p r o d u c t i o n of thin layers of
the
optically
active
garnet
Nd,Cr:Gd Sc2Ga Oi2
( N d , C r : G S G G ) , a v e r y efficient infrared lasing m e d i u m , w h i c h c o u l d offer exciting n e w possibilities a s
a n active w a v e g u i d e or m i c r o l a s e r if i n c o r p o r a t e d into
S i - t e c h n o l o g y . N d , C r : G S G G h a s a unit cell of 160
a t o m s a n d c o n t a i n s six different e l e m e n t s .
3
3
D e s p i t e its c o m p l e x c h e m i c a l a n d c r y s t a l l o g r a p h i c
n a t u r e , thin films of ( N d , C r : G S G G ) c o u l d be g r o w n
h e t e r o e p i t a x i a l l y o n S i ( 0 0 1 ) u s i n g P L D [5]. T h e l u m i n e s c e n c e p r o p e r t i e s of the films w a s e s s e n t i a l l y i d e n tical to t h a t of the bulk m a t e r i a l , s h o w n in Fig. 3.
105
IN-SITU S U R F A C E DIFFRACTION
T h e flexibility a n d p u l s e d n a t u r e of P L D a n d P R C L A
m a k e it an ideal t e c h n i q u e for in-situ s t u d i e s of thin
film g r o w t h u s i n g x - r a y diffraction. In the last year, a
d e d i c a t e d in-situ
facility for x-ray s t u d i e s of films
g r o w n by P L D a n d P R C L A in t h e S u r f a c e Diffraction
Station of the Materials S c i e n c e B e a m l i n e at the
S w i s s Light S o u r c e has b e e n d e s i g n e d . T h e facility
will c o n s i s t of a five-circle d i f f r a c t o m e t e r a n d a n ultrahigh v a c u u m P L D c h a m b e r
h i g h - p e r f o r m a n c e analytical
m a t e r i a l s s y n t h e s i s [6].
techniques
with
novel
F i g . 4 : O v e r v i e w of the c h a m b e r d e s i g n t o be u s e d for
in-situ s u r f a c e diffraction studies of n o v e l films a n d
s t r u c t u r e s g r o w n by P L D a n d P R C L A .
TRANSFER OF EQUIPMENT
i
650
f
i
i
t
i
700
i
t
i
f
t
750
i
i
i
I
i
i
i
800
i
I
i
850
I
I
I
900
wavelength [nm]
F i g . 3: L u m i n e s c e n c e s p e c t r a of N d , C r : G S G G e x c i t e d
by 4 4 2 - n m light f r o m a H e - C d laser. T h e t o p c u r v e is
for t h e P L D - g r o w n f i l m , the m i d d l e c u r v e is for the bulk
ablation target, a n d t h e b o t t o m c u r v e w a s r e c o r d e d for
excitation at g r a z i n g i n c i d e n c e t o t h e bulk s u r f a c e .
T h e differences in the s p e c t r a at 7 5 0 a n d 8 0 0 ~ n m are
e x p l a i n e d by self a b s o r p t i o n of f l u o r e s c e n c e in t h e
bulk a n d t h e r m a l p r o m o t i o n .
including a large b e r y l l i u m w i n d o w , w h i c h is t r a n s p a r ent t o x - r a y s a n d a l l o w s 190° a z i m u t h a l a n d 50° polar
s c a n n i n g of t h e diffracted signal. M o v e m e n t of t h e
s a m p l e s u r f a c e is p e r f o r m e d u s i n g a h e x a p o d a n d is
d e c o u p l e d f r o m t h e c h a m b e r b o d y by a rotation
feedthrough
and
edge-welded
bellows.
Sample
t r a n s f e r is p o s s i b l e w i t h o u t b r e a k i n g t h e v a c u u m by
using a load lock. A t e c h n i c a l d i a g r a m of the c h a m b e r
is s h o w n in Fig. 4 .
T h e a p p a r a t u s h a s b e e n d e s i g n e d t o be c o m p a t i b l e
with o t h e r e q u i p m e n t a n d b e a m l i n e s at t h e S L S ,
w h e r e i m p o r t a n t s y n e r g i e s are f o r e s e e n . T h i s facility
t h e r e f o r e r e p r e s e n t s a u n i q u e o p p o r t u n i t y of m a r r y i n g
T h e in-situ s t u d i e s will b e c o m p l e m e n t e d by ex-situ
film g r o w t h in a c o n t i n u a t i o n of w o r k p r e v i o u s l y c a r r i e d
out at t h e P h y s i c a l C h e m i s t r y Institute ( P C I ) of the
University of Z u r i c h . T h e ultra-high v a c u u m d e p o s i t i o n
e q u i p m e n t at t h e PCI w a s t r a n s f e r r e d in O c t o b e r 2 0 0 1
t o the S w i s s Light S o u r c e , a n d a s e c o n d n e w ex-situ
c h a m b e r h a s b e e n d e s i g n e d a n d is b e i n g c o n s t r u c t e d
for c o m p l e m e n t a r y r e s e a r c h to t h e in-situ
studies
mentioned above.
REFERENCES
[1]
E.W. P l u m m e r , Ismail, R. Matzdorf,
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106
APPEND X
PUBLICATIONS
P.A. A l e k s e e v , E.V. N e f e o d o v a , U. S t a u b , J . M . Mignot,
V.N. Lazukov,
P. S a d i k o v ,
L. S o d e r h o l m ,
S.R. W a s s e r m a n n , Y . B . P a d e r n o , N.Y. S h i t s e v a l o v a ,
A. M u r a n i , Low-Energy
Magnetic
Response
and Yb
Valence in the Kondo Insulator
YbB , P h y s . R e v . B
63, 064411 (2001).
G. L o d a , M. L o n z a , F. M a z z o l i , G. M i a n , N. P a n g o s ,
R. S e r g o ,
V. S m a l u k ,
R. T o m m a s i n i ,
L. T o s i ,
L. Z a m b ó n , M. Dehler, R. Ursic, First
Commissioning
Results
of the ELETTRA
Transverse
Multi-Bunch
Feedback,
Proc. D I P A C ' 0 1 , G r e n o b l e , F r a n c e , 6 6
(2001).
12
A. B a d e r t s c h e r ,
M. D a u m ,
P.F.A. G o u d s m i t ,
M. J a n o u s c h , P.-R. Kettle, J . K o g l i n , V . E . M a r k u s h i n ,
J . S c h o t t m ü l l e r , Z . G . Z h a o , Experimental
Verification
of Coulomb
de-excitation
in Pionic Hydrogen,
Europ h y s . Lett., 5 4 ( 2 0 0 1 ) .
J . Bahrdt,
W . Frentrup,
A. G a u p p ,
M. S c h e e r ,
W . G u d a t , G. Ingold, S. S a s a k i , Elliptically
Polarizing
Insertion
Devices
at BESSY
II, N I M A 4 6 7 - 4 6 8 , 21
(2001).
J . Bahrdt,
W . Frentrup,
A. G a u p p ,
M. S c h e e r ,
W . G u d a t , G. Ingold, S. S a s a k i , A Quasi-Periodic
Hybrid Undulator at BESSY II, N I M A 4 6 7 - 4 6 8 ( 2 0 0 1 ).
M. B ö g e , J . C h r i n , CORBA Objects for SLS
Subjects,
Proc. 3
Int. W o r k s h o p o n P e r s o n a l C o m p u t e r a n d
Accelerator Control Systems ( P C a P A C 2000), DESY,
Hamburg, Germany.
r d
J.H.H. Bongaerts,
M.J. Z w a n e n b u r g ,
F. Z o n t o n e
J . F . v a n der V e e n , Propagation
of Coherent X Rays in
a Multi-Step
Index Waveguide,
J. Appl. Phys. 90, 94
(2001).
C. Bressler,
M. S a e s ,
M. C h e r g u i ,
R. A b e l a ,
P. P a t t i s o n , Optimizing
a Time-Resolved
X-Ray
Absorption Experiment,
Nucl. I n s t r u m . M e t h . A 4 6 7 - 4 6 8 ,
1444 (2001).
C. Bressler,
M. S a e s ,
M. C h e r g u i ,
D. G r o l i m u n d ,
R. A b e l a , P. Pattison, Towards Structural Dynamics
in
condensed
Chemical
Systems
Exploiting
Ultrafast
Time-Resolved
X-Ray
Absorption
Spectroscopy,
J. C h e m . Phys. 116, 2955 (2001).
C. Bressler,
M. S a e s ,
M. C h e r g u i ,
R. A b e l a ,
D. G r o l i m u n d ,
P.A. H e i m a n n ,
R.W. S c h o e n l e i n ,
S.L. J o h n s o n , A . M . L i n d e n b e r g , R.W. F a l c o n e , High
sensitive
XAS WithSingle,
X-Ray
Pulses
at
1kHz,
C o m p e n d i u m of U s e r A b s t r a c t s a n d T e c h n i c a l R e ports 2 0 0 0 at t h e A d v a n c e d Light S o u r c e ( 2 0 0 1 ).
C. Bressler,
M. S a e s ,
M. C h e r g u i ,
R. A b e l a ,
R.W. F a l c o n e ,
P.A. H e i m a n n ,
S.L. J o h n s o n ,
A.M. Lindenberg,
R.W. S c h o e n l e i n ,
M. Hertlein,
Chemical
Dynamics
Applications
Exploiting
the Femtosecond
X-Ray
Beamline
5.3.1., C o m p e n d i u m of
U s e r A b s t r a c t s a n d T e c h n i c a l R e p o r t s 2 0 0 0 at t h e
A d v a n c e d Light S o u r c e ( 2 0 0 1 ).
C. B r ö n n i m a n n , R. Baur, E.F. E i k e n b e r r y , S. K o h o u t ,
M. Lindner, B. S c h m i t t , R. H o r i s b e r g e r , A Pixel ReadOut Chip for the PILATUS
Project, N u c l . Instr. M e t h .
Phys., Res. A 465, 235 (2001).
D. B u l f o n e , C.J. B o c c h e t t a , R. B r e s s a n u t t i , A. C a r n i e l ,
G. C a u t e r o ,
A. Fabris,
A. G a m b i t t a ,
D. G i u r e s s i ,
D. Bulfone,
R. B r e s s a n u t t i ,
M. L o n z a ,
L. Z a m b ó n ,
M. Dehler, The ELETTRA/SLS
Transverse
Multibunch Feedback,
Proc. S h a n g h a i S y m p o s i u m on Int e r m e d i a t e - E n e r g y Light S o u r c e s , S h a n g h a i , C h i n a ,
September 2001.
R. B r e s s a n u t t i ,
D. B u l f o n e ,
M. L o n z a ,
V. S m a l u k ,
L. Z a m b ó n , M. Dehler, R. Ursic Exploitation
of the
Integrated
Digital
Processing
and Analysis
of the
ELETTRA/SLS
Transverse
Multi-Bunch
Feedback
System, Proc. P A C 0 1 , C h i c a g o , U S A , 1 2 6 7 ( 2 0 0 1 ) .
T. D ü t e m e y e r , C. Q u i t m a n n , M. Kitz, K. D ö r n e m a n n ,
L.S.O. J o h a n s s o n , B. Reihl, Photoelectron
Imaging
Using an Ellipsoidal
Display Analyzer, Pev. Sei. Instr.
72, 2638 (2001).
M.K. Fix,
M. S t a m p a n o n i ,
P. M a n s e r ,
E.J. B o r n ,
R. Mini, P. R ü e g s e g g e r , A Multiple Source Model for
6 MV Photon Beam Dose Calculations
using
Monte
Carlo, Physics
in Medicine
and Biology, 4 6 , 1 4 0 7
(2001).
U. F l e c h s i g , L. Patthey, C. Q u i t m a n n , Extended
SX700 Type Monochromator
Combining
Normal
and
Grazing Incidence
Optics for a New Undulator
Beamline at SLS, N u c l . Instr. M e t h . A 4 6 7 - 4 6 8 , 4 7 9 ( 2 0 0 1 ) .
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for ABS
Applications, W o r k s h o p on A u t o m a t e d B e a m S t e e r i n g a n d
Shaping (ABS) 2 0 0 1 , San Jose, USA, 3.-4.12.2001.
J . C h r i n , On The Use of CORBA in High-Level
Software Applications
at the SLS, 8
ICALEPCS, San
Jose, CA, USA, 27.-30.11.2001.
t h
F. G o z z o , High Resolution
at the SLS Materials
Science Beamline
Powder
Endstation,
2
SLS Users
M e e t i n g , P S I , Villigen, S w i t z e r l a n d , 1 3 . - 1 5 . 1 1 . 2 0 0 1 .
n d
A. L ü d e k e , System Integration
of High Level
Applications during the Commissioning
of the Swiss
Light
Source, 8
ICALEPCS, San Jose, CA, USA, 27.30.11.2001.
t h
n d
U. S t a u b , Direct Observation
of 1-Dimensional
Charge
Order below the Metal-Insulator
Transition in Yb4As3,
6th E u r o c o n f o r e n c e o n Properties of C o n d e n s e d
Matter p r o b e d with X - r a y s c a t t e r i n g (Electron C o r r e l a tions
and
Magnetism),
Patras,
Greece,
21.25.09.2001.
U. S t a u b , Formation
of a Magnetic
Soliton Lattice in
CuB204,
S w i s s - D a n i s h W o r k s h o p o n N e u t r o n Scatt e r i n g , P S I , Villigen, S w i t z e r l a n d , 1 6 . - 1 7 . 1 0 . 2 0 0 1 .
A. S t r e u n , Commissioning
of the Swiss Light
Source,
Particle A c c e l e r a t o r C o n f e r e n c e 2 0 0 1 , C h i c a g o , U S A ,
18.-22.06.2001.
A. S t r e u n , Commissioning
of the Swiss Light
Source,
S h a n g h a i S y m p o s i u m o n Intermediate E n e r g y Light
Sources, Shanghai, China, 24.-26.09.2001.
A. S t r e u n , Beam Stability and Dynamic Alignment
at
SLS, S h a n g h a i S y m p o s i u m on I n t e r m e d i a t e E n e r g y
Light S o u r c e s , S h a n g h a i , C h i n a , 2 4 . - 2 6 . 0 9 . 2 0 0 1 .
A. S t r e u n , Commissioning
of the Swiss Light
Source,
9 A n n u a l W o r k s h o p on E u r o p e a n S y n c h r o t r o n Light
S o u r c e s ( E S L S 9), K a r l s r u h e , G e r m a n y , 8 . - 9 . 1 1 . 2 0 0 1 .
t h
J.F. v a n der V e e n , Status of the SLS, W o r k s h o p o n
Soft X - r a y S c a t t e r i n g in C o n d e n s e d Matter P h y s i c s ,
P S I , Villigen, S w i t z e r l a n d , 2 9 . - 3 0 . 0 3 . 2 0 0 1 .
J.F. v a n der V e e n ,
Die
Synchrotron
Lichtquelle
Schweiz, ein Neues Licht zur Erforschung
der Materie, Inaugural L e c t u r e , E T H Z u r i c h , 4 . 0 5 . 2 0 0 1 .
J.F. v a n der V e e n , Interface
Science
at the
Swiss
Light Source, 16. PSI T a g e s s y m p o s i u m E l e k t r o c h e m i s c h e E n e r g i e s p e i c h e r u n g , P S I , Villigen, Switzerland, 23.10.2001.
110
J . F . v a n der V e e n , Research
at the SLS or How to
Become a User, 2 S L S U s e r s M e e t i n g , P S I , V i l l i g e n ,
Switzerland, 14.-15.11.2001.
n d
P.R. W i l l m o t t , Future Trends for In-House Research at
the Surface
Diffraction
Station
at the Swiss
Light
Source
Materials
Science
Beamline.
X S D Meeting,
P S I , Villigen, S w i t z e r l a n d , 7 . 1 1 . 2 0 0 1 .
P.R. W i l l m o t t , Nonthermal
Thin Film Growth
at the
Surface Diffraction
Station at the SLS Source
Materials Science Beamline,
2
SLS Users Meeting, PSI,
Villigen, S w i t z e r l a n d , 1 3 . - 1 4 . 1 1 . 2 0 0 1 .
n d
POSTERS
F. D'Acapito, Charge
Order
Driven
Metal-Insulator
Transition in NdNi03, 2 0 0 1 S w i s s W o r k s h o p o n M a t e rials with N o v e l Electronic Properties, L e s Diablarets,
Switzerland, 1.-3.10.2001.
P. W y s s , M. S t a m p a n o n i , X-Ray
Tomographic
Microscopy (XTM) at the Swiss Light Source, S L S U s e r s
M e e t i n g , P S I , Villigen, S w i t z e r l a n d , 1 4 . - 1 5 . 1 1 . 2 0 0 1
P.R. W i l l m o t t , H. S p i l l m a n n , Gas-Phase
Mechanisms
in the Growth of ZrCyN-i.y Thin Films by Pulsed
Reactive Crossed-Beam
Laser Ablation,
Cola01 Conference on Laser Ablation, Tokyo, Japan, 4.10.2001.
S. Z e l e n i k a , F. De B o n a , Analytical
and
Experimental
Characterisation
of High-Precision
Flexural Pivots, 2
E U S P E N Int. Conf., T u r i n , Italy, 2 7 . - 3 1 . 0 5 . 2 0 0 1 .
n d
J.H.H. Bongaerts,
M.J. Z w a n e n b u r g ,
M. d e V r i e s ,
J . M i g u e l , U. F l e c h s i g , C. D a v i d , G. W e g d a m , J.F. v a n
der V e e n , Structure and Dynamics
of Colloidal
Fluids
Confined in a Planar X-Ray Waveguide,
Gordon Res e a r c h C o n f e r e n c e on X - R a y P h y s i c s , C o n n e c t i c u t ,
USA, 22.-27.07.2001.
C. G o u g h , M. M a i l a n d , Septum
and Kicker
Systems
for
the
SLS,
PAC'2001,
Chicago,
USA,
18.22.06.2001.
M. H o e s c h , M. Muntwiler, M. H e n g s b e r g e r , T. G r e b e r ,
J . O s t e r w a l d e r , Design of a Complete
Photoemission
Experiment,
V U V XIII C o n f e r e n c e , T r i e s t e , Italy,
24.07.2001.
A. L i i d e k e , Application
of Digital
Regulated
Power
Supplies
for Magnet
Control
at the Swiss
Light
Source, 8
ICALEPCS, San Jose, CA, USA, 27.30.11.2001.
t h
F. Nolting, A PEEM Study of Small Agglomerates
of
Colloidal
Iron Oxide Nanocrystals,
13* Int. Conf. o n
V a c u u m Ultraviolet R a d i a t i o n P h y s i c s , T r i e s t e , Italy,
23.-27.07.2001.
B.D. P a t t e r s o n , P.R. W i l l m o t t , F. G o z z o , R. A b e l a ,
J . F . v a n der V e e n , X-Ray Physics at the Swiss
Light
Source,
Gordon Research Conference on X-Ray
Physics, Connecticut, USA, 22.-27.07.2001.
TEACHING ACTIVITIES
B. P a t t e r s o n , Festkörperphysik
W S 2000/2001.
I, University of Z u r i c h ,
B. P a t t e r s o n , Festkörperphysik
SS 2001.
II, University of Z u r i c h ,
B. P a t t e r s o n , Festkörperphysik
W S 2001/2002.
I, University of Z u r i c h ,
C. Q u i t m a n n , Photoelectron
sanne, SS 2 0 0 1 .
Microscopy,
L. R i v k i n , J . Ulbricht, Teilchenbeschleuniger
tektoren
der
Hochenergiephysik,
W S 2001/2002.
H.J. W e y e r , Forschung
an
Synchrotronstrahlungsanlagen, University of B a s e l , S S 2 0 0 1 .
J.F. v a n der V e e n , Physik
W S 2001/2002.
I, E T H Z u r i c h ,
V. Schlott, C. D a v i d , A. J a g g i , A Zone Plate
Based
Beam
Monitor
for the Swiss
Light
Source,
DIPAC'2001, Grenoble, France, 13.-15.05.2001.
DIPLOMAS
M. S t a m p a n o n i , R. A b e l a , P. W y s s , P. R ü e g s e g g e r ,
Edge-Enhanced
Radiography
of Biological
Samples,
S L S I n a u g u r a t i o n , P S I ; Villigen, 1 9 . 1 0 . 2 0 0 1 .
U. S t a u b ,
G.I. Meijer,
F. F a u t h ,
R. A l l e n s p a c h ,
G. B e d n o r z , J . K a r p i n s k i , S. K a z a k o v , L. P a o l a s i n i ,
und DeETH Zurich,
L. R i v k i n , Beam Dynamics
with Synchrotron
Radiation, A c c e l e r a t o r P h y s i c s C o u r s e , C E R N A c c e l e r a t o r
S c h o o l , Seville, S p a i n , O c t o b e r 2 0 0 1 .
P.R. W i l l m o t t , Laser und Laserspektroskopie,
sity of Z u r i c h , S S 2 0 0 1 .
V. Schlott, M. D a c h , M. Dehler, R. K r a m e r t , P. Pollet,
T. Schilcher,
A. K o s i c e k ,
R. Ursic,
R. D e M o n t e ,
M. Ferianis, Commissioning
of the SLS Digital
BPM
System, P A C ' 2 0 0 1 , C h i c a g o , U S A ; 1 8 . - 2 2 . 0 6 . 2 0 0 1 .
Lau-
R. Reiser, Physik,
Abteilung Machinenbau, Hochs c h u l e für T e c h n i k , W i r t s c h a f t u n d V e r w a l t u n g , Z ü r i c h .
C. Q u i t m a n n ,
U. F l e c h s i g ,
F. Nolting,
L. Patthey,
T. S c h m i d t , G. Ingold, M. J a n o u s c h , R.Abela, J . F . v a n
der V e e n , A Beamline
for
Photoelectron-Microscopy
at the Swiss Light Source (SLS), 1 3 Int. Conf. V a c u u m Ultraviolet R a d i a t i o n P h y s i c s , T r i e s t e , 2 3 . 27.07.2001.
t h
EPF
Univer-
P.R. W i l l m o t t , Strukturaufklärung
in Physik,
Chemie,
und Biologie
mit Hilfe Synchrotronstrahlung
- Eine
Einführung, University of Z u r i c h , W S 2 0 0 1 / 2 0 0 2 .
S. K o h o u t , Messungen
am Auslesechip
für den PILATUS Detektor,
B e t r e u u n g : C. B r ö n n i m a n n . L e i t u n g :
H. Keller, University of Z u r i c h , W S 2 0 0 0 / 2 0 0 1 .
S. C. L e e m a n n , Precise Energy Calibration
Measurement at the SLS Storage Ring by Means of
Resonant
Spin Depolarization,
B e t r e u u n g : M. B o e g e , L. Rivkin.
L e i t u n g : R. Eichler, W S 2 0 0 1 / 2 0 0 2 .
D. S c h m i d i g , Hochauflösende
Szintillatoren
für Röntgen-Mikrotomographie
mit
Synchrotronstrahlung,
B e t r e u u n g : M. S t a m p a n o n i . L e i t u n g : P. R ü e g s e g g e r ,
ETH Zurich, W S 2000/2001.
111
M E M B E R S H I P S IN E X T E R N A L C O M M I T T E S
T. Pal
•
H.J. W e y e r
C o n s u l t i n g Editor, S y n c h r o t r o n R a d i a t i o n N e w s
O R A C L E Users Group, CERN-IT, Geneva
J.F. van der Veen
L. R i v k i n
•
EPAC2002, S P C Chairman, Organizing
tee
•
A P A C 2 0 0 1 , Scientific P r o g r a m C o m m i t t e e
•
E P S 1 2 , International P r o g r a m C o m m i t t e e
•
C E R N Accelerator School, Program Committee
•
Joint Universities
Committee
•
SOLEIL Machine Advisory Committee
•
W o r k i n g G r o u p of t h e G e r m a n S c i e n c e C o u n c i l
( W i s s e s c h a f t s r a t ) for t h e e v a l u a t i o n of t h e F E L
projects at D E S Y ( H a m b u r g ) a n d B E S S Y ( B e r l i n )
Accelerator
School,
Commit-
Program
•
S c i e n c e A d v i s o r y C o u n c i l for E L E T T R A ,
t r o n e T r i e s t e , Italy
•
Scientific C o m m i t t e e for Inorganic a n d A n a l y t i c a l
Chemistry, Science Foundation Flanders, Belgium
•
M e m b e r of R e v i e w P a n e l , A L S , Berkeley.
•
Editorial B o a r d of P r o g r e s s in S u r f a c e S c i e n c e
A. W r u l i c h
•
EPAC2002, SPC, Organizing Committee
•
T A C C h a i r m a n , T e c h n i c a l A d v i s o r y C o m m i t t e e for
D I A M O N D , UK.
•
Scientific A d v i s o r y C o m m i t t e e for B E S S Y II, Berlin,
Germany.
•
A d v i s o r y P a n e l for t h e E L E T T R A , T r i e s t e , Italy.
•
C o - E d i t o r of t h e ' J o u r n a l of S y n c h r o t r o n R a d i a t i o n ' .
•
International A d v i s o r y C o m m i t t e e for I N D U S II
•
Scientific C o u n c i l for D E S Y
V. S c h l o t t
•
DIPAC'2001, Program Committee
A. Streun
•
S h a n g h a i S y m p o s i u m on I n t e r m e d i a t e E n e r g y
Light S o u r c e s , P r o g r a m C o m m i t t e e , S h a n g h a i ,
China.
Sincro-
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