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SRL-ISSP, University of Tokyo Norio Nakamura. Activities on the Orbit Feedback System for the Super-SOR Light Source. 3rd International Workshop on Beam Orbit Stabilization - IWBS2004, Hotel Kirchbühl, Grindelwald, Switzerland, December 6-10, 2004. Super-SOR Project. - PowerPoint PPT Presentation
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Activities on the Orbit Feedback Systemfor the Super-SOR Light Source
SRL-ISSP, University of TokyoNorio Nakamura
3rd International Workshop on Beam Orbit Stabilization - IWBS2004, Hotel Kirchbühl, Grindelwald, Switzerland, December 6-10, 2004
Super-SOR Project
• The Super-SOR project aims to construct a 3rd-generation VUV and soft X-ray synchrotron radiation source in Japan.• Proposed site is in the new campus of the University of Tokyo (Kashiwa campus).
Plan View of Super SOR Light Source
ICCR&Four Centers
New Graduate School
Super SOR(planned)
ISSP
Super-SOR Accelerators
• Designed to meet top-up injection• Pre-Injector Linac: E=200MeV, Single- and Multi-bunch modes• Booster synchrotron : E=0.2-1.8GeV, x=50-100 nm rad Variable momentum compaction (=0.003-0.01) • Storage ring : E=1.8GeV, x=7-8 nm rad, I=400mA
1.8GeV Storage Ring
200MeV LinacÅ@
93.7m
81.1m
35m22m
1.8GeV Synchrotron
circumference: 280.55m
Å@
Super-SOR Storage Ring
• 14 DBA cells with 2 x 17m and 12 x 6.2m long straight sections• Flexible optics with high- and low-beta straight sections• Vertical beam size at insertion devices : y = 10 - 30 m
(a) High-beta mode
(b) Hybrid mode
Optics of half ring
Design Goal of Orbit Feedback System
• Fast and High-resolution Beam Position Measurement Resolution < 1 m @ sampling rate > 2 kHz
• Wide Frequency Range BW > 100Hz ( Noise attenuation: < -20dB @ 10Hz )
• High Position Stability at Insertion Devices New orbit correction scheme
Submicron Stability
Outline of Orbit Feedback System
140 BPM(10 BPM/cell)
70 FS(5 FS/cell)
Centralcontroller
Ring Control System
Localcontroller
Localcontroller
Localcontroller
Localcontroller
Localcontroller
Localcontroller
Localcontroller
Localcontroller
Localcontroller
Localcontroller
Localcontroller
Localcontroller
Localcontroller
Localcontroller
BPM
FS
FSFS
FS
FS
FSFS
FS
FS
FS
FS
FS
FS
FS
BPM
BPM
BPM
BPM
BPM
BPM
BPMBPM
BPM
BPM
BPM
BPM
BPM
Ethernet
Fast Data Transfer System(by Shared memory etc.)
FS:Fast Steering MagnetBPM:Beam Position Monitor
New Orbit Correction Scheme
Vector of residual COD:
(1)y : beam position before correction (M): kick angle of steering magnet (N)R : Response matrix (M x N)
Constraint conditions:
(2)
Minimize the norm of under the constraint conditions by introducing the following function of S (Lagrange’s method of indeterminate multipliers).
(3)
Set derivatives of the function S with respect to and to zero.
(4)(5)
Solution of the above equations:
(6)
where
(7) (8)
(9)
Definition of the matrix A-1 :
(NV N), (10)
vi : i-th eigenvector of the matrix Ai: i-th eigenvalue of the matrix A
For i~0, 1/i in the matrix A-1 is replaced with zero to avoid very large kick angles. The condition of NV NC is required for the existence of the inverse matrix P-1.
If z is taken as the electron (or photon) beam positions measured at arbitrarily selected BPMs (or photon BPM) and C as the corresponding response matrix, the beam positions at the selected BPMs are fixed at zero by this correction. For the electron beam and BPMs, Eq. (6) can be rewritten in a simplified form.
(11)
€
CiT ⋅θ + zi = 0 ( i = 1,LL , NC )
€
S =1
2( Rθ + y )2 + μ i (Ci
T
i
Nc∑ θ + zi )
€
R T Rr
θ + R T r y + C
r μ = 0
€
C Tr
θ +r z = 0
€
r= B
r y − D
r z
€
B= (− A−1 + A−1CP −1C T A−1 )R T
€
D = A−1CP −1
€
A= R T R
€
P = C T A−1C
€
A−1 =r v i
r v i
T
λ ii=1
Nv∑
€
r= B* y
Principle of eigenvector method with constraints (call “EVC” or “SVDC” here)
€
r≡ R
r θ +
r y
See Proceedings of EPAC98 and PAC99
Orbit Correction Simulation
Simulations confirm that the global and local corrections are compatible in the new method.
(1) COD sources are all the quadrupole magnets with vertical position errors of =50 m.(2) Constraint conditions are that positions at 28 BPMs on both sides of 14 long straight sections are zero.(3) 140 BPMs and 70 fast steering magnets are used for correction simulations.
-6
-4
-2
0
2
4
6
-0.06
-0.04
-0.02
0
0.02
0.04
0.06
0 50 100 150 200 250
Number of eigenvectors = 50
Before CorrectionAfter Correction
Length [m]
0.6
0.8
1
1.2
1.4
30 40 50 60 70
Max AngleRMS angle
Number of eigenvectors
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0 10 20 30 40 50 60 70
All BPMs
without constraintswith constraints
Number of eigenvectors
Orbit Correction Study at PF ring (1)
Experimental study of the new orbit correction method at PF ring
Outline of correction study1. Vertical COD is artificially generate
d by each vertical dipole and then several times corrected by 28 fast steering magnets using eigenvector methods with and without constraints. The number of the used eigenvectors is 14.
2. Constraint conditions are that beam positions at 4 BPMs on both sides of the two long straight sections are zero.
3. Measured response function is used.4. RMS CODs for the constrained 4 BP
Ms and for all the BPMs are obtained for the two kinds of correction methods.
VD12FS09 FS24
VD33BPM16BPM17
BPM50BPM49
PF ring (2.5GeV) 65 BPMs 4 constrained BPMs (BPM01,41,42,65) 28 Fast Steering Magnets(FSs) 42 Vertical Dipoles(VDs)
Orbit Correction Study at PF ring (2)Example of vertical COD before and after correction
-40
-20
0
20
40
-400
-200
0
200
400
0 10 20 30 40 50 60
with constraints (VD25)
after correctionbefore correction
.BPM No
-40
-20
0
20
40
-400
-200
0
200
400
0 10 20 30 40 50 60
without constraints (VD25)
after correctionbefore correction
.BPM No
Orbit Correction Study at PF ring (3)
1 m
Local correction performance of the new method is a sub-micron level !
Global correction performances of the two methods are almost the same.(The global correction performance for VD 40 - VD05 can easily be compensated by adding 1 or 2 steering magnets in the section.)
0
20
40
60
80
100
120
140
0 5 10 15 20 25 30 35 40
Constrained 4 BPMs with constraintswithout constraints
. No of VD used for COD generation
0.01
0.1
1
10
100
0 5 10 15 20 25 30 35 40
Constrained 4 BPMs with constraintswithout constraints
. No of VD used for COD generation
0
20
40
60
80
100
120
140
0 5 10 15 20 25 30 35 40
All BPM with constraintswithout constraints
. No of VD used for COD generation
0.01
0.1
1
10
100
0 5 10 15 20 25 30 35 40
All BPM
with constraintswithout constraints
. No of VD used for COD generation
1 m
Linear plot Log plot
Linear plot Log plot
Orbit Correction Study at PF-AR Ring (1)
Experimental study of the new orbit correction method at PF-AR ring
Outline of correction study1. Vertical COD is artificially genera
ted by each vertical dipole (VD) and several times corrected by the other 78 VDs using eigenvector methods with and without constraints. The number of the used eigenvectors are 40.
2. Constraint conditions are that positions at 6 BPMs on both sides of the three long straight sections are zero.
3. Measured response matrix is used.4. RMS CODs for the 6 BPMs and al
l the BPMs are obtained for the two kinds of correction methods.
VD20
VD19
VD61
VD62
VD60
VD59
VD21
VD22
BPM19
BPM20
BPM21
BPM22
BPM23 BPM61
BPM62
BPM63
BPM64
BPM65
PF-AR ring (6.5GeV) 83 BPMs (total) 6 constrained BPMs (BPM25,26,36,37,41,42) 79 Vertical Dipoles(VDs)
Orbit Correction Study at PF-AR Ring (2)
BPMResolution(~8m)
BPMResolution(~8m)
Local correction performance of the new method is better than BPM resolution.
Global correction performances of the two methods are almost the same.
0
10
20
30
40
50
60
0 10 20 30 40 50 60 70 80
Constrained 6 BPMs correction with constraintscorrection without constraints
. No of VD used for COD generation
0
10
20
30
40
50
60
0 10 20 30 40 50 60 70 80
All BPMs correction with constraintscorrection without constraints
. No of VD used for COD generation
BPM System (1)
Example of BPM location
Prototype of BPM support
BPMBellows
Absorber flange
SR
Cooling water
• BPM block (SUS) with SMA feedthroughs • Fixed on the girder by BPM support• Reduction of vacuum chamber stress by bellows • Protection from SR irradiation by absorber
Prototype of BPM block
BPM System (2)
Design of BPM Electronics using Multiplexing & Heterodyne method
ATT
ATT
ATT
ATT
SW BPF1
RFAMP1
BPF2
RFAMP2
ATT BPF3
IFAMP2DividerMIX1 MIX2
LPF
AMP
-3dB -3.5dB
-15dB +19.5dBNF=3dB
+19.5dBNF=3dB
0dB ~ -30dB +19dB
NF=6dB
BPMLO
-8dB
+40dB100kHz
-8dBLimit AMP
Bypass-0.5dB Bypass
-0.5dBBypass-0.5dB
fc=500MHz
• S/N is more than 90dB at 200mA ( < 0.3m in resolution).
• Single-bunch operation is also considered.
• BPM signals can be switched to another system for turn-by-turn measurement.
PROBLEMS
• Position error by coherent synchrotron oscillations
• Cost effectiveness
Another type of BPM electronics is also under consideration.
Fast Steering Magnet System (1)
Prototype of Fast Steering MagnetPower Supply Models for Fast Steering Magnets Upper : Switching type Lower : Linear amp. type
• Fast steering magnet is made of 0.5-mm silicon steel laminations.• Two types of power supply (linear amp. and switching types) are tested.• Linear amp. type is superior to switching type in ripple noise.
Fast Steering Magnet System (2)
Steering magnet + Bellows ductMeasured frequency response
• All the fast steering magnets are installed on the RF-shielded bellows ducts.• Bellows duct is made of stainless steel and RF shields of 0.4mm-thick BeCu. • Effects of bellows on frequency response are negligibly small.
-5
-4
-3
-2
-1
0
1
2
-100
-80
-60
-40
-20
0
20
40
1 10 100 1000
Gain(without bellows)Gain(with bellows)
Phase(without bellows)Phase(with bellows)
Frequency[Hz]
Feedback Control System (1)
Local controller x 2 (prototype model) Block diagram of local controller
• Target feedback period Ts < 0.5ms (sampling rate > 2 kHz)• 140 BPM data are shared with all the controllers by a shared memory network.• CPU board computes beam positions at 10 BPMs and coil currents of 5 FSs.
Feedback Control System (2)
Measurement result of consumed time for each feedback process
Feedback period of less than 0.2 ms can be achieved.
Tim
e[s
ec]
Feedback process
BP
Mread
ing P
I con
trol
Position
calcu
lation M
atrixcalcu
lation D
ata tran
sfer T
otalS
teeringsettin
g
Noise Attenuation
-60
-50
-40
-30
-20
-10
0
10
1 10 100 1000
Gain(Ts=0.5ms)Gain(Ts=0.2ms)
Frequency(Hz)
Closed loop gain
Frequency Bandwidth > 100Hz
Summary
• An orbit feedback system is planned for the Super-SOR project to suppress the brilliance reduction due to orbit drifts and vibrations. Final goal is sub-micron stability at the source points and at the experimental stations.
• A new orbit correction method, the eigenvector method with constraints (“EVC” or “SVDC”), can unite global and local orbit feedbacks and enhance the beam stability at insertion devices up to a sub-micron level. We will try to stabilize photon beams using this correction method and photon BPMs.
• Design and R&D of the BPM, fast steering and feedback control systems are in progress. The feedback system can achieve position resolution of less than 1m and the frequency bandwidth of more than 100 Hz.