1. Studies of cERL injector
48th ICFA Advanced Beam Dynamics Workshop on Future Light Sources
Studies of cERL injector
Thursday, March 4, 2010 SLAC National Accelerator Laboratory Menlo Park, California
Tsukasa Miyajima
7th division, Accelerator Laboratory,
KEK, High Energy Accelerator Research Organization
Contents
Outline of compact ERL injector
Beam Simulation to optimize beamline parameters
Test beamline for cERL injector
Future issues
Summary
I’m tsukasa miyajima, in KEK, High energy accelerator research organization.
Today, I will be talking about Studies of compact ERL injector in KEK.
These are contents of my talk.
Firstly, I will show you outline of compact ERL injector.
In the ERL injector, optimization of beamline parameters is important to obtain smaller emittance and shorter bunch length..
I will show you beam simulation to optimize beamline parameters.
Then, I will show you test beamline for cERL injector, and future issues
Finally, I summarized my talk.

2. ERL collaboration team
High Energy Accelerator Research Organization (KEK)
M. Akemoto, T. Aoto, D. Arakawa, S. Asaoka, A. Enomoto, S. Fukuda, K. Furukawa, T. Furuya, K. Haga, K. Hara, K. Harada, T. Honda, Y. Honda, T. Honma, T. Honma, K. Hosoyama, M. Isawa, E. Kako, T. Kasuga, H. Katagiri, H. Kawata, Y. Kobayashi, Y. Kojima, T. Matsumoto, H. Matsushita, S. Michizono, T. Mitsuhashi, T. Miura, T. Miyajima, H. Miyauchi, S. Nagahashi, H. Nakai, H. Nakajima, E. Nakamura, K. Nakanishi, K. Nakao, T. Nogami, S. Noguchi, S. Nozawa, T. Obina, S. Ohsawa, T. Ozaki, C. Pak, H. Sakai, S. Sakanaka, H. Sasaki, Y. Sato, K. Satoh, M. Satoh, T. Shidara, M. Shimada, T. Shioya, T. Shishido, T. Suwada, T. Takahashi, R. Takai, T. Takenaka, Y. Tanimoto, M. Tobiyama, K. Tsuchiya, T. Uchiyama, A. Ueda, K. Umemori, K. Watanabe, M. Yamamoto, Y. Yamamoto, S. Yamamoto, Y. Yano, M. Yoshida
Japan Atomic Energy Agency (JAEA)
R. Hajima, R. Nagai, N. Nishimori, M. Sawamura
Institute for Solid State Physics (ISSP), University of Tokyo
N. Nakamura, I Itoh, H. Kudoh, T. Shibuya, K. Shinoe, H. Takaki
UVSOR, Institute for Molecular Science
M. Katoh, M. Adachi
Hiroshima University
M. Kuriki, H. Iijima, S. Matsuba
Nagoya University
Y. Takeda, T. Nakanishi, M. Kuwahara, T. Ujihara, M. Okumi
National Institute of Advanced Industrial Science and Technology (AIST)
D. Yoshitomi, K. Torizuka
JASRI/SPring-8
H. Hanaki
This list shows members for compact ERL collaboration team in Japan.
FLS2010, March 1-5, 2010,
SLAC National Accelerator Laboratory
Tsukasa Miyajima

3. The Compact ERL for demonstrating ERL technologies
Before constructing large-scale ERL facility, we need to demonstrate the generation of ultra-low emittance beams using key devices.
Compact ERL
Parameters of the Compact ERL
Parameters
Beam energy
MeV
Injection energy
5 MeV
Average current mA
Acc. gradient (main linac)
15 MV/m
Normalized emittance
mm·mrad
Bunch length
(rms)
1 - 3 ps (usual)
~ 100 fs (with B.C.)
RF frequency
1.3 GHz
East Counter Hall
Before constructing large-scale ERL facility, we need to demonstrate the generation of ultra-low emittance beams using key devices.
The compact ERL will be constructed in KEK to demonstrate reliable operations of the key components such as gun and superconducting cavity and to demonstarate high current operation.
This photo graph shows KEK, and the cERL will be constructed in the East Counter Hall.
This figure shows the layout of cERL in the Ease Counter Hall.
This list shows the parameters of compact ERL
The beam energy at main linac is greater than 35 MeV, the beam current greater than 10mA. normalized emittance 1 to 0.1 mm mrad.
In order to clear this condition, we employed photocathode DC gun to generate high brightness, high current electron beam with emittance lower than 1 mm-mrad and current greater than 10mA.
100 m
FLS2010, March 1-5, 2010,
SLAC National Accelerator Laboratory
Tsukasa Miyajima

4. SLAC National Accelerator Laboratory
cERL injector
cERL injector: to generate electron beam with lower emittance and shorter bunch length
Parameters of the Compact ERL Injector
Beam energy
5 – 10 MeV
Beam current
10 – 100 mA
Normalized rms emittance en = e/(gb)
1 mm·mrad (77 pC/bunch)
0.1 mm·mrad (7.7 pC/bunch)
Bunch length (rms)
1 – 3 ps (0.3 – 0.9 mm)
Photo cathode DC gun
Super conducting cavity
(2 cell, 3 modules)
ERL Injector
Merger section
The purpose of compact ERL injector is to generate electron beam with lower emittance and shorter bunch length.
This table shows parameters of the compact ERL injector.
Beam energy, beam current, emittance, bunch length.
The ERL injector is here.
It consists of roughly 3 parts, Photo cathode DC gun, super conducting cavity, and merger section.
Next I will show you components in ERL injector.
Compact ERL
FLS2010, March 1-5, 2010,
SLAC National Accelerator Laboratory
Tsukasa Miyajima

5. Components in ERL injector
Photo cathode DC gun
Gun, HV power supply, driving laser system
Solenoid magnet
To compensate emittance
Bunching cavity
Normal conducting cavity for bunching
SRF cavities
2-cell, 3 modules
Quadrupole magnets
To adjust CS parameters before merger section
Merger section
To merge injected beam into return loops ② ① ⑤ ⑥
There are 6 components in the ERL injector.
Photo cathode DC gun to generate electron beam.
We use solenoid magnet to compensate emittance.
To make shorter bunch length, we use normal conducting bunching cavity.
To accelerator beam energy from 500 keV to 5 MeV ore more, 2-cell 3moducles SRF cavity are used.
After SRF cavities, 5 quadrupoles are arranged to adjust CS parameters.
To adjust CS parameters in this area is important to obtain smaller emittance at the exit of merger.
Final section of the injector is merger section. ③ ④
Beam energy:
500 keV
5 – 10 MeV
Space charge effect is dominant.
FLS2010, March 1-5, 2010,
SLAC National Accelerator Laboratory
Tsukasa Miyajima

6. Cross sections and field maps
(a) Cross sections
DC gun
Solenoid magnet
Bunching cavity
SRF cavity
(b) 1D field map
These are cross sections and field maps for beam simulation.
FLS2010, March 1-5, 2010,
SLAC National Accelerator Laboratory
Tsukasa Miyajima

7. Physics in ERL injector
Space charge effect （Coulomb force between electrons)
Solenoid focusing （Emittance compensetion）
RF kick in RF cavity
Higher order dispersion in merger section
Coherent Synchrotron Radiation (CSR) in merger section
Response time of photo cathode（It generates tail of emission.）
These effects combine in the ERL injector.
To obtain high quality beam at the exit of merger, optimization of beamline parameters is required.
Method to research the beam dynamics:
Macro particle tracking simulation with space charge effect is used.
The simulation code have to include
External electric and magnetic field,
Space charge effect (3D space charge).
In the injector, we have to treat these effects.
Space charge effect, solenoid focusing, RF kick, higher order dispersion, CSR and response time of photo cathode.
Because these effects combine in the ERL injector, optimization of beamline parameters is required to obtain high quality beam.
To study beam dynamics in the injector, we use macro patciel tracking simulation with space charge effect.
FLS2010, March 1-5, 2010,
SLAC National Accelerator Laboratory
Tsukasa Miyajima

8. SLAC National Accelerator Laboratory
Beam Simulation
Purpose of simulation
To find optimum beamline parameters, i.e. magnet strength, RF phase, etc., with lower emittance and shorter bunch length.
To calculate beam parameters, i.e. emittance, beam size, etc., to design components in ERL injector.
Beam energy
5 – 10 MeV
Beam current
10 – 100 mA
Normalized rms emittance en = e/(gb)
1 mm·mrad (77 pC/bunch)
0.1 mm·mrad (7.7 pC/bunch)
Rms bunch length (rms)
1 – 3 ps (0.3 – 0.9 mm)
Initial distribution on cathode：beer-can
Purposes of simulation are to find optimum beamline parameters with lower emittance and shorter bunch length, and to calculate beam parameters to design components in the ERL injector.
As particle tracking code, GPT is used. It has 3D space charge calculation.
As an initial particle distribution generated on cathode surface, we used ideal shape, beer-can distribution.
Particle tracking code：GPT(General Particle Tracer)[1]
Space charge calculation：3D mesh based method
Initial particle distribution：beer-can
No CSR effect in merger section
d = 4 sx
[1] Pulsar Physics, 　
Dt=sqrt(12)*st
FLS2010, March 1-5, 2010,
SLAC National Accelerator Laboratory
Tsukasa Miyajima

9. Multi objective optimization
To minimize both emittance and bunch length at 1 m from the exit of merger
Multi objective method is used[2]
Results of optimization
Bunch length vs. normalized rms emittance
For shorter bunch length, emittance is larger than the case of longer bunch length.
Layout of beamline
Beam parameters are calculated at 1 m from exit of merger.
Normalized rms emittance
0.4 ～ 0.5 mm mrad
Free parameters in the optimization
Initial laser radius (mm)
Initial laser pulse length (ps)
Magnetic field of 1st solenoid
Electric field of bunching cavity
Magnetic field of 2nd solenoid
Electric field and phase of SRF1
Electric field and phase of SRF2
Electric field and phase of SRF3
Magnetic fields of 5 quadrupoles
We optimize beam quality at 1 m from the exit of merger.
These are free parameters in the optimization. We have 16 knob to adjust.
This graph shows trade-off solutions calculated by multi objective method.
For shorter bunch length, emittance is larger than the case of longer bunch length.
Number of free parameters: 16
Minimize both emittance and bunch length. (2 objects optimization)
[2] Ivan V. Bazarov and Charles K. Sinclair ,
Phys. Rev. ST Accel. Beams 8, (2005).
FLS2010, March 1-5, 2010,
SLAC National Accelerator Laboratory
Tsukasa Miyajima

10. Dependence on number of particles
In the macro particle tracking simulation, we can not avoid the effect of number of macro particles, because we can not simulate actual number of electrons.
To obtain more accurate results,
In early optimization : 5k particles　（to save CPU time）
But, the accuracy is not so good for 5 k particles
In final optimization, we optimize beam line parameters with 200 k particles after the early optimization with 5k particles.
For 77 pC, actual number of electrons is 480 M particles.
Normalized rms emittance
Rms beam size
In the macro particle tracking simulation, we can not avoid the effect of number of macro particles, because we can not simulate actual number of electrons.
For 77 pC beam, actual number of electrons is 480 M particles.
To obtain more accurate results, we have 2 steps in the optimization.
In early optimization, we uses 5 k macro particles to save CPU time.
In the final optimization, we use 200 k macro particles and the initial parameters calculated by early optimization with 5 k macro particles.
These graph show dpendenc on number of particles.
It shows 5 k macro particles are not enough.
At least, 100 k macro particles are required.
At lease Nps > 100 k
FLS2010, March 1-5, 2010,
SLAC National Accelerator Laboratory
Tsukasa Miyajima

11. Optimum beamline parameters
Beam line parameters for high current mode with 80 pC/bunch, which give bunch length of 0.63 mm and normalized rms emittance of 0.56 mm mrad
Next, I show optimum beamline parameters.
The bunch length is 0.63 mm, and normalized rms emittance is 0.56 mm mrad.
*:RF phase from maximum acceleration.
FLS2010, March 1-5, 2010,
SLAC National Accelerator Laboratory
Tsukasa Miyajima

12. Time evolution of beam parameters
(2) Rms beam size and bunch length
(1) Normalized rms emittance
(3) Kinetic energy and energy spread
These graphs show time evolution of beam parameters.
Emittance, rms beam size, bunch length, and energy.
Normalized rms emittance： 0.56 mm mrad
Bunch length：0.63 mm
Kinetic energy：8.2 MeV
Related rms energy spread: 0.23 %
FLS2010, March 1-5, 2010,
SLAC National Accelerator Laboratory
Tsukasa Miyajima

13. Time evolution of phase space distribution
cathode
Bunch charge: -80 pC/bunch
Normalized rms emittance：
　　0.56 mm mrad
Bunch length：0.63 mm
Kinetic energy：8.2 MeV
1st solenoid
Exit of merger
Bunching cavity
2nd solenoid
Exit of SRF
5 quadrupoles
These graphs show transverse phase space plots.
At the exit of merger, we get these values.
FLS2010, March 1-5, 2010,
SLAC National Accelerator Laboratory
Tsukasa Miyajima

14. Summary of optimization
We have designed the injector for the cERL and carried out beam dynamics simulation using the particle tracking code with 3D space charge effect.
To optimize the beamline parameters, we are using multi objective method and cluster linux machine.
At the end of the injector, we have obtained the emittance of 0.56 mm·mrad with the bunch length of 0.63 mm for the high current operation mode (80 pC/bunch).
This is short summary of optimization.
FLS2010, March 1-5, 2010,
SLAC National Accelerator Laboratory
Tsukasa Miyajima

15. Gun test beamline for cERL injector
Purpose of test beam line
To gain operation experience of the low energy beam.
To evaluate performance of the DC guns by an additional diagnostic line to measure emittance and bunch length
To develop a new 500 kV gun, diagnostic system and the injector line used at cERL.
2010- middle of 2011: 200 kV gun
: new 500 kV gun
NPES3, 200 kV gun
transferred from Nagoya university at May 2009.
Gun Test beamline
Laser system
Next, I will show you test beamline for cERL injector.
Since last year, we started construction of the test beamline.
Porpose of test beamline is
To gain operation experience of the low energy beam.
To evaluate performance of the DC guns by an additional diagnostic line to measure emittance and bunch length.
To develop a new 500 kV gun and the injector line used at cERL.
This is layout of gun test area.
Now, there is a 200 kV gun developed Nagoya university for ILC polarized electron source.
This gun was transferred from Nagoya university at May 2009.
Middle of 2011, we will use 200 kV gun to test the beam diagnostic system.
After construction of 500 kV gun, we will use the new 500 kV gun.
Test area for 500 kV gun
FLS2010, March 1-5, 2010,
SLAC National Accelerator Laboratory
Tsukasa Miyajima

16. Layout of gun test beamline
5th view screen
3rd solenoid
4th solenoid
1st slit
(horizontal)
2nd slit
(horizontal)
1st slit
(vertical)
2nd slit
(vertical)
1st solenoid
2nd solenoid
Beam dump
1st view screen
This is layout of test beamline.
This region has the same layout as cERL injector.
After this region, we connect beam diagnostic line, which have double slit emittance measurement system and deflecting cavity to measure bunch length.
And, this is beam dump line.
2nd view screen
3rd view screen
4th view screen
Bending magnet
deflector
The same layout as cERL injector
Beam diagnostic line (emittance,
Bunch length measurements)
Beam dump line
FLS2010, March 1-5, 2010,
SLAC National Accelerator Laboratory
Tsukasa Miyajima

17. Components for gun test facility
We are constructing gun test facility with 200 kV photo cathode DC gun in AR south experimental hall, KEK. From this spring, we are going to start beam running.
2nd solenoid
From Gun e-
To SRF cavity e-
Bunching cavity
2nd view screen monitor
Two solenoid magnets
1st view screen monitor
1st solenoid
Laser chamber
We are constructing gun test facility with 200 kV photo cathode DC gun in AR south experimental hall, KEK. From this spring, we are going to start beam running.
This figure shows the cERL injector beam line before SRF cavity.
These two photograph show two solenoid magnets and laser chamber.
The layout of the cERL injector before SRF cavity.
In the first test, the bunching cavity is not installed.
Laser chamber
FLS2010, March 1-5, 2010,
SLAC National Accelerator Laboratory
Tsukasa Miyajima

18. Beam dynamics of gun test beamline
Result of optimization
Initial parameters at point A:
Radius of initial particle distribution：　　1.91 mm
Laser pulse full width：41.5 ps
1st Solenoid：0.039 T
Bunching cavity： 0 kV
2nd Solenoid：0.026 T A
At 1st slit,
Emittance: 0.42 mm mrad
Bunch length: 6.7 mm
Gun
1st view screen
2nd view screen
I show you beam dynamics in the gun test beamline.
This graph show result of optimization.
At the 1st slit, the minimum emittance is calculated to be 0.42 mm mrad with longer bunch length.
These two graphs are the time evolutions of beam parameters.
And, these graphs are transverse phase space distribution.
1st slit
3rd view screen
FLS2010, March 1-5, 2010,
SLAC National Accelerator Laboratory
Tsukasa Miyajima

19. SLAC National Accelerator Laboratory
Future issues
Beamline parameter optimization for XFEL-O with 20 pC, 0.1 mm mrad.
To obtain lower emittance, can we increase the voltage of the photo cathode gun over 500 kV?
Beam optics matching with return loop
Establish the beam tuning method in the commissioning.
Beam simulation with CSR and Space charge effect in the merger section. We developed CSR routine, which is effective in lower energy beam.
R. Hajima and N. Nishimori (JAEA), Proc. FEL2008, pp
cf. K.-J. Kim et al., PRL 100, (2008).
Finally, I will show you future issues for the beam dynamics in cERL injector .
1st issue is optimiation for XFEL-O. XFEL-O requires 0.1 mm mrad with 20 pC. It is challenging.
2nd is beam optics matching with return loop.
3rd is establith the beam tuning method in the commissioning with lower beam energy.
4th is beam simulation with CSR and space charge.
FLS2010, March 1-5, 2010,
SLAC National Accelerator Laboratory
Tsukasa Miyajima

20. Beam simulation for XFEL-O
Target values for XFEL-O: < 0.1 mm mrad, 20 pC/bunch, 2 ps bunch length
Layout of beamline
Preliminary results
Bunch charge: 20 pC/bunch
Gun voltage: 500 kV or 600 kV
(1) 0.6 mm (2 ps) bunch length
enx = 0.14 mm mrad with 500 kV
enx = 0.13 mm mrad with 600 kV
(2) 0.9 mm (3 ps) bunch length
enx = 0.12 mm mrad with 500 kV
enx = 0.11 mm mrad with 600 kV
Beam parameters are calculated at 1 m from exit of merger.
Preliminary results
For XFEL-O, we are optimizing beam line parameters.
The target values for XFEL-O are less than 0.1 mm mrad with 20 pC/bunch and 2 ps.
This graph shows preliminary results with different gun voltages, 500 kV and 600 kV.
For 2 ps beam, the emittances are 0.14 mm mrad with 500 kV and 0.13 mm mrad with 600 kV.
It is not so far from target value for XFEL-O.
We are going to investigate the effect of gun voltage.
It is not so far from target value for XFEL-O.
We are going to investigate the effect of gun voltage.
FLS2010, March 1-5, 2010,
SLAC National Accelerator Laboratory
Tsukasa Miyajima

21. SLAC National Accelerator Laboratory
Summary
Beam dynamics simulation for the cERL has been carried out using 3D space charge macro-particle tracking code.
To find the optimum parameters, which give minimum emittance and bunch length, the parameter optimization has been carried.
For high current mode with 80 pC/bunch, we obtained the minimum emittance of 0.56 mm mrad with the bunch length of 0.63 mm.
To design ERL components (Gun, Buncher, SRF cavities, solenoid, alignment, etc.), we have studied tolerances of errors in ERL injector.
To evaluate performance of the DC guns, we are developing the gun test beamline in the PF-AR south experimental hall.
From the early part of March, we are going to start beam running in the gun test beamline using NPES3 200kV DC photo cathode gun.
For XFEL-O, the minimun emittance is calculating with 20 pC/bunch.
So far, we have obtained the minimum emittance of 0.13 mm mrad with the bunch length of 0.6 mm (2 ps) and the gun voltage of 600 kV.
This is summary of my talk.
Thank you for your attention.
FLS2010, March 1-5, 2010,
SLAC National Accelerator Laboratory
Tsukasa Miyajima

22. SLAC National Accelerator Laboratory
Backup slides
FLS2010, March 1-5, 2010,
SLAC National Accelerator Laboratory
Tsukasa Miyajima

23. SLAC National Accelerator Laboratory
Effect of gun voltage
Preliminary results
Bunch charge: 20 pC/bunch
Gun voltage: 500 kV or 600 kV
At exit of merger
(1) 0.6 mm (2 ps) bunch length
enx = 0.14 mm mrad with 500 kV
enx = 0.13 mm mrad with 600 kV
(2) 0.9 mm (3 ps) bunch length
enx = 0.12 mm mrad with 500 kV
enx = 0.11 mm mrad with 600 kV
Results of Gun and solenoid beamline
FLS2010, March 1-5, 2010,
SLAC National Accelerator Laboratory
Tsukasa Miyajima

24. How to optimize the parameters?
Macro particle tracking simulation with space charge requires longer CPU time.
In the optimization, tracking simulation is repeated to search optimum parameter. Therefore, the calculation time to optimize the parameters is too long.
To save the calculation time, efficient optimization method is required.
In order to reduce the calculation time, we use
Multi objective method [2] as an efficient method, and
Cluster linux computer, which have 80 CPUs. The parallel 80 jobs, which have different beamline parameters, can be executed on the cluster computer.
Two objects in the optimization
Emittance
Bunch length
To minimize emittance and bunch length
In our case, we have to minimize both emittance and bunch length.
In multi objective method, we choice two objects, emittance and bunch length.
To minimize emittance and bunch length becomes trade-off solutions.
Trade-off solutions
[2] Ivan V. Bazarov and Charles K. Sinclair ,
Phys. Rev. ST Accel. Beams 8, (2005).
FLS2010, March 1-5, 2010,
SLAC National Accelerator Laboratory
Tsukasa Miyajima

25. Results of optimization
(1) Sector type（bending angles：-19, 22, -19 degree)
Normalized rms emittance
0.4 ～ 0.5 mm mrad
(2) Rectangular type（bending angles：-16, 16, -16 degree)
Emittance growth caused by space charge dispersion.
The rectangular type gives smaller emittance than the sector type. It seems that stronger longitudinal space charge dispersion in the sector type causes the difference of emittance, because the bending angle of the bending magnet in the sector type (19◦ or 22◦) are larger than one in the rectangular type (16◦).
In this case, we investigate the effect of merger type.
We designed two types of merger, which have same injection angle.
1st merger consists of sector type magnets, and 2nd merger consists of rectangular type magnet.
Sector type has larger bending angles to satisfy achromatic condition at the exit of merger.
This graph shows the results.
Rectangular type gives lower emittance.
We decide to use rectangular type merger.
Maximum emittance growth
Minimum emittance growth
Emittance growth depends on space charge dispersion.
FLS2010, March 1-5, 2010,
SLAC National Accelerator Laboratory
Tsukasa Miyajima

26. Beam parameter with 7.7 pC/bunch
Charge: 7.7 pC/bunch
Emittance: mm mrad (horizontal), mm mrad(vertical)
Bunch length: 1.3 ps
R. Hajima, et. al., “Design Study of the Compact ERL”
PF-ISAC Light Source Subcommittee
25 February, 2009

27. PF-ISAC Light Source Subcommittee
1D CSR routine in GPT
(2) Emittance growth caused by CSR
We developed 1D CSR routine, which is effective in lower energy beam, e.g. beam energy of 10 MeV.
Based on Sagan’s formula[4]
Layout of beamline
(1) Energy loss due to CSR
Using the CSR routine, we can calculate CSR effect in lower energy region, e.g. beam enegy of 10 MeV.
PF-ISAC Light Source Subcommittee
25 February, 2009

28. Tolerance of errors in ERL injector
Tolerances of errors in ERL linacs are important to design ERL components (Gun, Buncher, SRF cavities, solenoid, alignment, etc.).
For example, to design LLRF system, tolerances of phase and amplitude error are required.
The tolerances were calculated using numerical space charge simulation code, GPT.
In this presentation, we show variations of
Arrival time
Transverse emittance
Kinetic energy
at the end of merger, when gun voltage, RF amplitude or phase are varied.
Amplitude error in RF cavity
Phase error in RF cavity
Next, I will show you tolerance study in ERL injector.
PF-ISAC Light Source Subcommittee
25 February, 2009

29. PF-ISAC Light Source Subcommittee
Errors in ERL injector
Misalignment
Emittance growth
Orbit distortion
Laser timing jitter
Ripple of gun HV source
Arrival time
Kinetic energy
Amplitude error in RF cavities
Phase error in RF cavities
Bunch length
Photo cathode DC gun
Misalignment, laser timing jitter, ripple of gun HV source
Solenoid magnet
Misalignment, field error
Bunching cavity
Misalignment, amplitude and phase error
SRF cavities
Quadrupole magnets
Merger section
Arrival time delay is occurred by varying kinetic energy and R56. ② ① ⑤ ⑥ ③ ④
500 keV
5 – 10 MeV
PF-ISAC Light Source Subcommittee
25 February, 2009

30. Example: Ripple of Gun HV source
Arrival time
0.1% error: -120 fs
Normalized rms emittance
±0.1% error: fluctuation of 3.5 %
Kinetic energy
0.1% error: 99.96%
PF-ISAC Light Source Subcommittee
25 February, 2009

31. Results of tolerance calculations
Difference of arrival time at exit of merger becomes about 100 fs.
The arrival time includes the effect of R56 in the merger section.
Gun ripple
RF amplitude
RF phase
Error
0.1 %
0.1 degree
Difference of arrival time
-120 fs
-100 fs
Kinetic energy
99.96 % %
99.98 %
Emittance
3.5 %
(for ±0.1% error)
1.5 %
(for ±0.1 % error)
2.5 %
(for ±0.1 degree error)
From the above results, we decided the requirement for design of components, as following;
Gun HV ripple < 0.1 %
Error of RF amplitude < 0.1 %
Error of RF phase < 0.1 degree
PF-ISAC Light Source Subcommittee
25 February, 2009

32. Problem of space charge calculation in merger
Merger section
Original routine (spacecharge3dmesh)
　　　⇒　calculated emittance is not correct.
It is clear for smaller number of particles.
We checked the source code.
Injected beam
Beam goes forward along the following orbit.
Calculated emittance depends on angle from z-axis.
Why?
orbit
（in drift space）
emittance

33. Enhanced space charge calculation in GPT
In original spacecharge3dmesh routine,
　　　direction of mesh box：fixed to coordinate in GPT
When beam go forward along oblique line fro z-axis,
　　　mesh size becomes coarse.
We made enhanced routine　⇒ spacecharge3dmeshxz

34. Original
Enhanced routine
Spacecharge3dmeshxz
The enhanced routine can calculate the accurate emittance.

35. Misalignment of solenoid
Misalignment of solenoid position and angle
The beam parameters are calculated at exit of SRF cavities.

36. Result 1: Ripple of Gun HV source
Arrival time
0.1% error: -120 fs
Normalized rms emittance
±0.1% error: fluctuation of 3.5 %
Kinetic energy
0.1% error: 99.96%
10 June, 2009
ERL09

37. Timing in buncher
10 June, 2009
ERL09

38. Result 2: Amplitude error in RF cavities
Arrival time
0.1% error: -100 fs
SCA02
Normalized rms emittance
±0.1% error: fluctuation of 1.5 %
Kinetic energy
0.1% error: %
SCA03
10 June, 2009
ERL09

39. Result 3: Phase error in RF cavities
Arrival time
0.1% error: -120 fs
SCA01
Normalized rms emittance
±0.1 deg. error: fluctuation of 2.5 %
Kinetic energy
0.1% error: 99.98%
BCA01
10 June, 2009
ERL09