Beam Stabilization using Energy Compression System in SPring-8 Linac

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15 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

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SPring-8 Linac
Beam Stabilization using Energy Compression System in SPring-8 Linac
Japan Synchrotron Radiation Research Institute (JASRI)
Takao Asaka
Stability of the rf equipment
Fluctuation of the klystron beam voltage -> Adjustment of deQing circuit
Phase of klystron drive system -> Adjustment of the air conditioner
Phase of the klystron -> Continuous regulation type of cooling system
10deg./4˚C (10hrs periodical) -> <1deg./1˚C
2.4deg./3˚C (27min periodical) -> <0.5deg./0.5˚C
0.3% (rms) -> 0.04% (rms)
Stability of the beam energy
Stability of the beam current
Stability of the beam energy
>1% -> 0.06% (rms)@4hrs, 0.03% (rms)@10min
>20% -> 1.9% (rms)
Energy Compression system
Stability of the beam energy
0.03% (rms) -> 0.01% (rms)
SPring-8 Linac
Beam parameter and rf system of the SPring-8 linac
SynchrotronNew SUBARU
Peak current~ 200 mA~ 2 A~ 140 mA
Energy spread± 0.2 %± 0.3 %± 0.8 %
Normarized emittance (90%)
<200 π mm mrad<240 π mm mrad<160 π mm mrad
Bunch length15 ~25 psec15 ~25 psec15 ~25 psec
Beam energy (Maximum)1 GeV1.2 GeV1.2 GeV
Pulse width40 nsec1 nsec1 nsec
SPring-8 Linac
0.5
%
1.0
%
beam current
beam pulse width
center energy
energy spread
1.9A(peak)@LSBT
1nsec
1GeV
<0.5%
Beam loading at the accelerating structure
99
4
99
5
99
6
99
7
99
8
99
9
100
0
0123
Beam energy [MeV]
Bunch numbe
r
bunch length : 10pse
c
bunch spacing : 350pse
c
total charge : 1.9
A
0.24%
Accelerating structure
2π/3 mode constant gradient
Operation frequency
2856 MHz
Number of cell81
Shunt impedance
54 MΩ/m
Unloaded Q
13500
Effective length2.88 m
Filling time610 nsec
Input power (usual operation)
35MW
Total number
25
SPring-8 Linac
Beam timing jitter (rms): 6.8 psec
Energy acceptance of the synchrotron: ±1.0 %
Energy acceptance of the New SUBARU: ±0.2 %
The required time jitter of the synchrotron: ±100 psec
The required time jitter of the New SUBARU: ±50 psec
Compression factor : 25 deg./%
Bunch length
Energy spread
: 20psec -> 50 psec
: 1 % -> 0.5%
Compression factor of ECS
@beam current : 5A
: 1nsec@beam pulse width
SPring-8 Linac
Energy compression diagram
SPring-8 Linac
Energy stabilization & control by ECS
Center energy dependence on the phase
of the ECS
350psec
Accelerating strucure1 GeV chicane
Energy fluctuation
Time
Energy
Energy dependence on the phase of ECS
0.35% / 1deg.
Stability of the excitation current for chicane magnet< 1e-4
Stability of the phase of ECS< 0.5 deg. (rms)
0.0
0.1
0.2
0.3
0.4
0.5
980
990
1000
1010
1020
1030
-60-40-200204060
y = 998.8 + 0.34514x R= 0.99975
dE/E [%] (rms) with ECS
Center energy [MeV] (rms)
Phase [deg]
dE/E
Center Energy
Initial dE/E : 0.5% (rms)
Vacc=6.86MV/m
40°
SPring-8 Linac
Simulation of the energy compression
Beam loading effect of the ECS's
3 m long accelerating structure
: ~5A (peak to peak
)
Beam current
Beam pulse width: 1nse
c
Energy spread:±0.3% with ECS
Phase shift: < 3deg.
0
0.5
1
1.5
2
2.5
3
0
20
40
60
80
100
120
02468101214
dE/E [%] (peak to peak)
Bunch length [deg] (full width)
after ECS
Beam current (peak to peak) [A]
Bunch length
dE/E without ECS
dE/E with ECS
Initial bunch length : 10 psec (full width)
0
2
4
6
8
10
0
2
4
6
8
10
02468101214
Phase shift [deg]
Vacc [MV/m]
Beam current (peak to peak) [A]
Beam pulse width : 1 nsec
Vacc
3 bunches
2 bunches
SPring-8 Linac
Energy compression System (ECS)
3 m long accelerating
structure of ECS
1 GeV chicane
rectangular magnets
Schedule
1999/1~Calculation of the input power and phase
of ECS' acc.
1999/2~Design of low power rf system
1999/7~8
Installation and mesurement of the low power
rf system
1999/10~Design of high power rf system
2000/6~8Installation and mesurement of the high power
rf system
2000/10/31~Beam test
2000/10/10~17rf aging
2001/3~Operation start
SPring-8 Linac
Energy monitor at chicane section
Optical transition radiation (OTR) monitor@1 GeV chicane section (η = -1 m)
Kapton foil
thickness
: 12.5 m
Vacuum evaporation
: 0.4 m (aluminum)
( Al + Kapton foil target ) + φ80 mm telecentric lens + Random shutter camera
70mm
Deterioration in the
emittance with OTR monito
r
Injection beam current
5e -8 ~ 3e -7 m rad -> 5e -7 m rad@1 GeV
beam loss : negligible
SPring-8 Linac
-1%
+1%
+2%
+3%
-2%
-3%
OTR monitor at chicane section
: 1nsec
Beam current : 1.5A
Beam pulse width
Energy stabilizaton : 0.06% (rms)
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
012345
energy data 9/29/01
Beam energy [%]
Time [hours]
SPring-8 Linac
Block diagram of the RF system for ECS
SPring-8 Linac
Characteristics of the PLL for the Drive line of ECS
-30
-20
-10
0
10
20
30
40
24
25
26
27
28
29
30
31
4/9/01
21:00:00
4/9/01
22:00:00
4/9/01
23:00:00
4/10/01
0:00:00
4/10/01
1:00:00
4/10/01
2:00:00
data01 ECS DL PLL 4/9/01
Phase [deg]
Temperature [deg]
Phase [deg.]
Temperature [
˚
C]
date [m/d/y H:M:S]
PLL on
-4
-3
-2
-1
0
1
2
6/8/01 0:00:006/12/01 0:00:006/16/01 0:00:006/20/01 0:00:00
Phase [deg]
Date [m/d/y H:M:S]
PLL on
0.1deg (rms)
Phase correction
@PLL module
PLL off
Booster klystron stop
-30
-20
-10
0
10
20
30
40
25
26
27
28
29
30
31
32
4/10/01
20:00:00
4/10/01
21:00:00
4/10/01
22:00:00
4/10/01
23:00:00
4/11/01
0:00:00
4/11/01
1:00:00
data02 ECS DL PLL 4/10/01
Phase [deg.]
Temperature [deg]
Phase [deg.]
Temperature [
˚
C]
date [m/d/y H:M:S]
PLL off
SPring-8 Linac
Stability of the high power rf component for ECS
SPring-8 Linac
Beam test of ECS
beam pulse width
40nsec
1nsec
beam pulse width
0
2
4
6
8
10
11/2/00 0:40:0011/2/00 0:44:0011/2/00 0:48:0011/2/00 0:52:00
Beam current [mA]@Sy DCCT
Date [m/d/y H:M:S]
ECS off
ECS on
dE/E :1.4% (full width)
dE/E :3.5% (full width)
0
1
2
3
024681012
dE/E [%] measurement
dE/E [%] calculation
dE/E [%]
Energy gain [MV/m]
0
1
2
3
024681012
dE/E [%] measurement
dE/E [%] calculation
dE/E [%]
Energy gain [MV/m]
SPring-8 Linac
Measurement of the beam energy stability
-0.05
0
0.05
0.1
372
372
373
374
374
05101520
Vpulse@M18 & energy 10/4/01
energy [%]
Vpulse@M18 [kV]
Beam energy [%]@PM3-LS
Vpulse@M18 klystron[kV]
Time [minutes]
0.998
0.9985
0.999
0.9995
1
1.0005
1.001
1.0015
1.002
1.00068
1.00074
1.0008
1.00086
1.00092
05101520
Vpulse@M18 & energy 10/4/01
energy (auto correlation)
Vpulse (auto correlation)
energy (auto correlation)
Vpulse (auto correlation)
Time [minutes]
-0.5%
+0.5%
Beam current (peak): 200 mA
Beam pulse width: 1 nsec
Energy stabilization
: < 0.01% (rms)
SPring-8 Linac
Summary
The installation of the ECS were completed in
summer of 2000.
As results of rf measurement of ECS, it could operated
with the phase stability of 0.5deg. (rms).
The energy stability with ECS reached to 0.01% (rms).
In operation of long time, energy stability improves
from 0.06% to 0.01% by using the ECS.
SPring-8 Linac
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Stability of the energy and energy spread in accelerator facilities
SLC Linac0.03% (jitters(rms)), without feedback control [1]
1.5% (day - night) [2, 3]
-> rf amplitude and phase as the source of drift
KEK 8 GeV Linac0.1% (jitters(p-p)) [4]
MIT/Bates 1 GeV Linac0.4% -> 0.01% (rms) with feedback control [5]
SPring - 8 1 GeV Linac> 1% -> 0.01% (rms) with ECS