Transcript www.synchrotron.org.au

Top-Up WS, Melbourne (7-9 Oct. 09)
Top-Up Experience at SPring-8
K. Soutome
on behalf of
SPring-8 Acc. Group
0.03%
1
Historical Overview
Early Experiment:
SORTEC (1990) S.Nakamura et al., EPAC90, p.472
:
Test-Operation:
SRRC (1996)
T.S.Ueng et al., EPAC96, p.2477
APS (1998)
L.Emery and M.Borland, PAC99, p.200
:
User-Operation:
APS (2001)
L.Emery et al., PAC01, p.2599
SLS (2001)
A.Ludke and M.Munoz, EPAC02, p.721
New-SUBARU (2003) and SPring-8 (2004)
H.Tanaka et al., J. Synch. Rad. 13 (2006) 378
:
Injection with ID Gap Closed and Photon Shutter Open
Now planned, tested and realized in many SR facilities
2
Status of SPring-8
total stored current
100 mA
injection current
~ 30 A
total current stability
~ 0.03 %
injection interval
15 sec ~ 3 min.
bunch current irregularity
< 10 %
impurity of single bunch
~ 10-9 (after 10 days)
3
Status of
SR Facilities
of the World
H.Ohkuma,
Proc. of
EPAC08, p.36
4
Merit of Top-Up Operation
• Short beam lifetime can be compensated.
• Photon source becomes more brilliant effectively.
• Experiments are free from normalization by current
and interruption for injection.
• Beam diagnostics is free from current dependence.
• Photon beam becomes stable owing to constant heat
load and thermal equilibrium of X-ray beam optics.
5
Issues
• Control of Total Current
• Control of Bunch Current (Filling Pattern )
• Suppression of Stored Beam Oscillation
• High Injection Efficiency
• High Purity of Single-Bunch
• Reliability of Injector
• Radiation Safety and Interlock
6
SPring-8 Site
8GeV XFEL Linac
(under construction)
© RIKEN/JASRI
1 - 1.5GeV Storage Ring
New-SUBARU
Booster Synchrotron
1GeV Linac
June 2009
Switching Magnet
8GeV Storage Ring
E = 8GeV, C = 1436m, I = 100mA
 = 3.4nmrad (with Dispersion Leakage)
DB Lattice with four 30m-LSSs
e7
Operation Scheme
1GeV Linac
Energy Compression System (ECS) with Chicane
Stability of Energy: 0.03%, Energy Spread (FWHM): 0.5%
Switching Magnet
New-SUBARU Ring
Booster Synchrotron
Ramping from 1 to 8 GeV at 1Hz
RF-KO for Single-Bunch
Beam Collimation in Transport Line
Top-Up Injection at 1GeV
or
Ramping to 1.5 GeV
8GeV Ring
Top-Up Injection with Oscillation Suppression of Stored Beam
Variation of Stored Current < 0.03%
Filling with Arbitrary Pattern (h=2436)
Impurity of Single Bunch < a few * 10**(-9)
8
Ring with 48-Cell Structure
Beam
from
Booster
Ring = [ ( Normal Cell ) ´ 9
+ ( Matching Cell )
+ ( Long Straight )
+ ( Matching Cell ) ] ´ 4
Beam is injected at the
normal straight section.
9
Beam Parameters
= 3.4nmrad (3nmrad when ID Gaps Closed)= 0.2%
x [m]
y [m]
x [m]
x [m]
y [m]
Normal Straight
22.6
5.6
0.107
301
6
30m-Long Straight
21.7
14.1
0.103
294
10
10
SPring-8 Storage Ring
Standard ID
30m-LSS
Experimental Hall
Long Undulator
11
Insertion Devices
Insertion Devices: Total 32
In-Vacuum Type ... Total 24
Standard Type ... Total 12
( = 32mm, N=140, Min.Gap(Full)=8mm, Kmax=2.5 )
ID24: Figure-8
ID19: 25m-Long Planner ( = 32mm, N=780 )
ID20: Narrowest Gap (Min. 7mm)
Out-Vacuum Type ... Total 8
ID08: Elliptical Wiggler ( = 120mm, N=37, Kymax=10 )
ID15: Revolver (Planner/Helical)
ID17: Combination of Permanent Magnets and Electromagnets with Iron-Poles
Fast Switching of Helicity, Figure-8 (Symmetric/Asymmetric)
ID25: Helical Tandem, Fast Switching with Bump Orbit (1-10Hz)
ID27: Figure-8
* Vertical aperture (full) is 15mm.
12
Issues
• Control of Total Current
• Control of Bunch Current (Filling Pattern )
• Suppression of Stored Beam Oscillation
• High Injection Efficiency
• High Purity of Single-Bunch
• Reliability of Injector
• Radiation Safety and Interlock
13
Filling Mode
Filling Mode
Bunch Current
Lifetime
multi-bunch (160 bunch-train x 12)
0.05 mA
~ 200 hr
203 bunches
0.5 mA
25 ~ 30 hr
0.3 mA
35 ~ 50 hr
4 bunch-train x 84
11 bunch-train x 29
1/7-filling + 5 single bunches
2.8 mA (single)
1/14-filling + 12 single bunches
1.6 mA (single)
18 ~ 25 hr
2/29-filling + 26 single bunches
1.4 mA (single)
4/58-filling + 53 single bunches
1.0 mA (single)
Multi-Bunch Mode : 17%
Several-Bunch Mode : 52%
Hybrid Mode
: 31%
Total Current: 100mA
14
RF and Injector
• RF Parameter:
– RF Frequency: 508.58 MHz
– Harmonic Number: 2436 (= 2x2x3x7x29)
• Injector: Single Bunch Operation
– 1 ns Gun Pulser
– Deflector (to eliminate dark current) @ Linac
– RF-KO System (bunch purifier) @ Booster
• Timing System: bucket selectable
15
Interval between Injection
~ Oct. 2007 : "Interval Prior" Mode
fixed interval
1min. for several- and hybrid-bunch mode
(5min. for multi-bunch mode)
Nov. 2007 ~ : "Current Prior" Mode
variable interval
1 shot per injection
16
Stability of Total Current
Stability of total current has been improved
from 0.1% to 0.03%.
interval prior mode
current prior mode
99.54
Stored Current [mA]
99.52
99.50
99.48
99.46
99.44
99.42
99.40
99.38
99.52
99.50
99.48
99.46
99.44
99.42
99.40
6:10
6:08
6:06
6:04
6:02
11/9/07
6:00
6:10
6:08
6:06
6:04
99.38
6:02
10/6/07
6:00
Stored Current [mA]
99.54
17
Notification of Injection Timing to Users
• We broadcast next injection time via
database system.
• We also deliver pre-trigger of beam
injection 1 msec before injection, but
users have never used this signal.
(Stored beam is very stable.)
18
Bucket Selection Scheme
Multi-Bunch Mode
in order of bucket number
Several-Bunche Mode
in order of bunch current
Hybrid Mode
in order of bunch current,
single-bunch section first
In several-bunch and hybrid mode filling
we measure the bunch current at all RF
buckets before each injection.
19
Voltage [V]
Bunch Current Measurement
• Button pick-up electrodes
– Sum of signals from two electrodes in
diagonal (to eliminate the effect of
betatron motion).
• Oscilloscope (Textronix DPO70404)
0.05
– analog bandwidth 4 GHz
0
– sampling rate 25 Gs/s
– measurment time 2 s
-0.05
– averaging 100 times
-0.1
-1.0
-0.5
0
0.5
1.0
Time [ns]
peak height and position
of each bucket by fitting on oscilloscope
1.5
2.0
20
Bunch Current
Users' Requirement on Uniformity:
Bunch Current Irregularity < 10 %
Cycle 07-03 203 bunches
15
(Imax - Imin) / I ave [%]
Bunch Current [mA]
0.54
~ 0.04 mA
0.52
0.50
0.48
0.46
6/7
0:00
2:00
4:00
6:00
Cycle 07-03 203 bunches
10
5
0
6/5
6/6
6/7
6/8
6/9
6/10
Top-up injection current is fixed to 30 A / shot.
21
Issues
• Control of Total Current
• Control of Bunch Current (Filling Pattern )
• Suppression of Stored Beam Oscillation
• High Injection Efficiency
• High Purity of Single-Bunch
• Reliability of Injector
• Radiation Safety and Interlock
22
Oscillation of Stored Beam at Injection
Main Sources of Oscillation
Horizontal
Nonlinear Kick by Sextupoles within Bump Orbit
Non-Similarity of Magnetic Field of Bump Magnets
Leakage Field from Septum Magnets
Vertical
Tilt of Bump Magnets
23
Oscillation of Stored Beam at Injection
Nonlinear Kick by Sextupoles within Bump Orbit
Magnet Arrangement of Injection Section
kick by sextupole magnets B1''x1(t)2: B2''x2(t)2: B3''x3(t)2: B4''x4(t)2
bump orbit x1: x2: x3: x4 = fixed in the first order approximation
==> Additional oscillation due to sextupole kicks can be canceled
(localized) by setting appropriate sextupole strength ratio.
H. Tanaka, et al., NIMA 539 (2005) 547
24
Oscillation of Stored Beam at Injection
Non-Similarity of Magnetic Field of Bump Magnets
Two Kinds, Four Bump Magnets
Long (BP1, 4)
We adjusted trigger-timing
and pulse-width but
non-negligible difference
remained.
Short (BP2, 3)
Trev = 4.8s
25
Oscillation of Stored Beam at Injection
Non-Similarity of Magnetic Field of Bump Magnets (cont.)
New Magnets with Non-Metallic End-Plates to Reduce Eddy Current
BP1
BP1EX
Coil
SUS End-Plate
Non-Metallic
End plate
Stack of 0.1mm
Electromagnetic Steel
26
Oscillation of Stored Beam at Injection
Leakage Field from Septum Magnets
Non-uniform leakage field generates
amplitude-dependent kick.
==>
Coil shape was improved and
field clamps were added at both
ends of magnets.
Septum-plane shields were extended
and their thickness was increased.
K. Tsumaki, et al., IEEE Trans. Appl. Superconductivity 14 (2004) 433
27
Oscillation of Stored Beam at Injection
Oscillation Measurement with Turn-by-Turn BPMs
Turn-by-turn BPM: located in dispersive section per 2 cells
max. 4096 turns with 10um reproducibility
First Kick
Second Kick
revolution: 4.8us
28
Residual Oscillation
Horizontal Osc. (meas.)
2009/07/30
29
Residual Oscillation
30
Residual Oscillation
31
Residual Oscillation
Horizontal Osc. (meas.)
2009/07/30
32
Residual Oscillation
33
Residual Oscillation
34
Residual Oscillation
35
Residual Oscillation
36
Residual Oscillation
37
Residual Oscillation
38
Residual Oscillation
39
Residual Oscillation
40
Residual Oscillation
41
Residual Oscillation
42
Residual Oscillation
43
Residual Oscillation
44
Residual Oscillation
45
Residual Oscillation
46
Residual Oscillation
47
Residual Oscillation
48
Residual Oscillation
49
Residual Oscillation
50
Residual Oscillation
51
Residual Oscillation
52
Residual Oscillation
53
Residual Oscillation
54
Residual Oscillation
55
Oscillation of Stored Beam at Injection
Estimation of Error Field
• Store a single-bunch beam.
• Fire bump magnets.
• Measure beam oscillation turn by turn.
• Assume that a dominant error kick is generated by one of four
bump magnets and calculate its strength by fitting.
• Repeat above by changing trigger-timing of bump magnets.
• Temporal variation of error kick is then obtained.
• If this error kick has a similar shape to the field of the bump
magnet (t), adjust its strength.
If this error kick has a shape of d(t)/dt, adjust its timing.
56
Oscillation of Stored Beam at Injection
Tilt-Adjustment for Suppressing Vertical Oscillation
• Estimate vertical error kick by using turn-by-turn
oscillation data.
• Adjust tilt angle of the bump magnet.
• Repeat until the residual oscillation becomes small.
Though this works, it is not easy, and so ...
Installation of Remote Tilt-Controller (Aug. 2007)
by K. Fukami
57
Oscillation of Stored Beam at Injection
Correction of Residual Oscillation
Feedforward Correction with Pulsed Corrector Magnets
(Arbitrary Waveform Generator + Amplifier)
Horizontal Corrector
Installed at Cell #48
Single-Turn Coil with Ceramics Chamber
10urad, 50A
5us
Voltage Amp (Yokogawa, 10MHz 75V 2A)
+ Current Buffer Amp
Vertical Corrector
Installed at Cell #2
Two-Turn Coil with Ceramics Chamber
1urad, 5A
Current Amp (APEX microtech PA05,
45V 30A 100V/us)
by T.Ohshima
58
Oscillation of Stored Beam at Injection
Amplitude of residual oscillation has now become small
compared to beam size.
Horizontal
Vertical
59
Oscillation of Stored Beam at Injection
Photon Beam Stability at Injection
NB: Damping Time of Betatron Oscillation: 8.3ms
60
Oscillation of Stored Beam at Injection
More on Stored Beam Oscillation
• Bump magnet yoke is of C-type and horizontal field is generated.
So, the vertical COD should be corrected carefully.
• Bunch-by-bunch feedback (BBF) is also effective for suppressing
stored beam oscillation. T. Nakamura, et al., EPAC04, p.2646
Beam Size at Injection Timing by Visible Light Interferometer
averaged over 1ms after injection timing
61
Issues
• Control of Total Current
• Control of Bunch Current (Filling Pattern )
• Suppression of Stored Beam Oscillation
• High Injection Efficiency
• High Purity of Single-Bunch
• Reliability of Injector
• Radiation Safety and Interlock
62
Injection Efficiency
• A limit is set to the following from radiation safety
(per operation cycle):
Total Number of Electrons Used for Top-Up Injection
Total Number of Electrons Lost during Top-Up Injection
• Electrons lost at insertion devices will cause
demagnetization of undulator magnets.
To keep high injection efficiency is important.
• Beam Collimation in Transport Line
• Low Chromaticity Operation
• Beta-Distortion Correction
• Stability of Injection Orbit
• Gap of In-Vacuum Undulator
63
Injection Efficiency
Beam Collimation in Transport Line
Horizontal Beam Scrapers for Top-Up Injection
 = 1. 249mm
 = 0. 544mm
K. Fukami, et al., APAC04, p.103
• In Top-Up Injection: +1
• Injection beam position can become closer to storage ring.
64
Injection Efficiency
Low Chromaticity Operation
Bunch-by-bunch feedback system enabled us to lower the
chromaticity of the ring.
Injection Efficiency as a Function of Gap Height of
25-m Long Planner In-Vacuum Undulator
65
Injection Efficiency
Beta-Distortion Correction
Beta-distortion was corrected by using 48 auxiliary quadrupole
power supplies.
Beta-function was obtained by response matrix analysis and
correction performance was checked.
Injection efficiency was improved by about 10%.
Momentum acceptance was also improved from 2.6% to 2.9%
and so the Touschek beam lifetime became longer.
66
Injection Efficiency
Horizontal Beta Correction
before (rms distortion: 7.4%)
* Half of the Ring is shown.
after (rms distortion: 1.9%)
67
Injection Efficiency
Vertical Beta Correction
before (rms distortion: 7.3%)
after (rms distortion: 1.5%)
68
Injection Efficiency
Injection Efficiency vs Beta Distortion
Injection Beam: Collimated
69
Injection Efficiency
Stability of Injection Orbit
Beam Position Measured with Optical Transition Radiation (OTR)
Monitor at the End of Transport Line
Data includes
Statistical
Errors.
• Stability of Magnet Power Supplies for Transport Line: +0.01%
• Position Stability of Beam from Booster: Order of 0.01mm
70
Injection Efficiency
In-Vacuum ID Gap
Capture Efficiency for 25-m Long Planner In-Vacuum Undulator
Gap Height (Full): 50mm - 12mm
Experiment
Simulation
71
Injection Efficiency
In-Vacuum ID Gap (cont.)
Effective Height of Vacuum Vessel
at the Largest Vertical Betatron Function
Tail of the particle desity seems to have
a dependence of y-2 during the damping
process.
M. Takao, et al., EPAC04, p.417
72
Injection Efficiency
Demagnetization of Undulator Magnets
In SPring-8 storage ring we have not observed any evidence of
demagnetization yet. ... Annealing is important.
Experiments using electron beam from booster synchrotron.
T. Bizen, et al., NIMA 574 (2007) 401, and refs. therein
73
Issues
• Control of Total Current
• Control of Bunch Current (Filling Pattern )
• Suppression of Stored Beam Oscillation
• High Injection Efficiency
• High Purity of Single-Bunch
• Reliability of Injector
• Radiation Safety and Interlock
74
Purity of Single Bunch
106
5
10
104
3
10
2
10
1
10
0
10
Impurity * 10
• Impurity of target bunch
after 10 days ~ 10-9
Impurity of injected
beam ~ 5 x 10-11
target
1.5mA
1*10 -9
3*10 -10
-1
0
1
Relative Bucket Number
20
-10
• Bunch purity monitor
– photon counting
– fast shutter (extinction
factor 10**-5)
10th day
Count
• Bunch cleaning system
@ injector
15
front bucket
rear bucket
10
5
0
0
2
4
6
8
Days
10
12
75
Issues
• Control of Total Current
• Control of Bunch Current (Filling Pattern )
• Suppression of Stored Beam Oscillation
• High Injection Efficiency
• High Purity of Single-Bunch
• Reliability of Injector
• Radiation Safety and Interlock
76
Statistics
• Mean Time between
Interruptions
– 11 hours
• Main Sources of
Interruption
– Linac mod. fault 1/3
– booster rf down 1/4
– booster rfko fault
– bunch cur. meas.
Interruption of Top-Up Operation '06
06-06
Linac Gun
Linac Mod
Linac Mag
Sy RF
Sy Mag
Sy etc
SR Mag
Control
etc
06-05
06-04
06-03
06-02
06-01
0
20
40
60
80
100
• Record: 6 days w/o
interruption
77
Issues
• Control of Total Current
• Control of Bunch Current (Filling Pattern )
• Suppression of Stored Beam Oscillation
• High Injection Efficiency
• High Purity of Single-Bunch
• Reliability of Injector
• Radiation Safety and Interlock
78
Radiation Safety
Charge-Loss Monitor Using CT in Transport Line and
DCCT in Storage Ring for Monitoring
(i) Total Number of Electrons Used for Top-Up Injection
and
(ii) Total Number of Electrons Lost during Top-Up Injection
Interlock
• Injection Electron Loss (hardware limit)
– Limit: 22 mA (6.6 x 1011 electrons) per 8 hours
• Injection Efficiency Monitor (software limit)
– Top-up injection stops
if 10 injection average < 50 %
or if 3 successive injections < 20 %
79
Radiation Safety
A power supply for storage ring bending magnets is
connected to a bending magnet in the transport line.
... This is to prevent high-energy electrons to go directly
into the experimental hutch located near the injection point
when the bending magnet power suppliy is accidentally
switched off.
Ring
Transport Line
Bending BL
80
Future Plan
(i) Further Suppression of Stored
Beam Oscillation
Fast kicker system is
under development.
Pulse Width < 1s
(ii) Use of Pulsed Q or SX as an Auxiliary
Device to Bump Magnets
Oscillation amplitude of an injected beam will be
reduced and injection efficiency will be increased.
The scheme is different from that with only Pulsed Q or SX:
K.Harada et al., PRST-SB 10 (2007) 123501
H. Takaki et al., Proc. of EPAC08, p.2204
81