LINAC2014 - List of Authors (Asaka, T.)

Paper	Title	Page
TUPP105	Storage Ring as a Linac Beam Monitor – Its Operation and Contribution to the Stable Top-up Injection	668
	Y. Shoji LASTI, Hyogo, Japan T. Asaka, H. Dewa, H. Hanaki, T. Kobayashi, Y. Minagawa, A. Mizuno, T. Shinomoto, S. Suzuki, Y. Takemura, T. Taniuchi, K. Yanagida JASRI/SPring-8, Hyogo-ken, Japan
	We have used the electron storage ring, NewSUBARU, as a beam monitor of the SPring-8 linac. The time and transverse profiles of the injected linac beam are recorded in a frame of a dual-sweep streak camera. A measurements through synchrotron or betatron oscillation in the ring gives multi-dimensional beam structure. The system functions as a final check of the linac beam. It gives the time profile and energy profile or transverse emittance, which includes Twiss parameters. It measures parameters of one linac bunch in a long macro pulse. A shot-by-shot measurement gives beam fluctuations. We report how we use the system and its contribution to the stable top-up operation. The beam loading effect on the bunch energy was obtained by bunch-by-bunch energy profile measurements. It confirmed the optimization of the ECS (Energy Compression System) parameters. The single shot bunch-by-bunch vertical emittance measurement proved the difference between the front bunch and the following bunches. The same measurement showed a timing jitter of the electron gun pulse although the rf synchronization was perfect. This jittering had made the injection efficiency unstable.

MOPP093	Evaluation of Beam Energy Fluctuations Caused by Phase Noises	273
	H. Hanaki, H. Dewa, S. Suzuki, K. Yanagida JASRI/SPring-8, Hyogo-ken, Japan T. Asaka, T. Ohshima RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
	The SSB noises of the RF reference signal dominate the short-term instabilities of the RF phase of the carrier RF. This phase modulation finally results in beam energy fluctuation. This presentation gives a quantitative evaluation of the beam energy fluctuations in an electron linear accelerator caused by phase noises, comparing a theoretical analysis and experimental results. A simple model was introduced to understand how phase noises result in the relative phase difference between a beam bunch and accelerating RF fields. In the experiments, we measured the enhanced beam energy fluctuations by modulating the phase of the reference RF signals with an external signal. The interference between the accelerating RF phase modulation and the timing modulation of a beam bunch was found in the model analysis and also in the experimental results.

MOPP094	Latest Improvements of the SPring-8 Linac for High Reliability	276
	S. Suzuki, H. Dewa, H. Hanaki, T. Kobayashi, T. Magome, A. Mizuno, T. Taniuchi, K. Yanagida JASRI/SPring-8, Hyogo-ken, Japan T. Asaka RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
	In order to perform stable injection to the 8GeV SPring-8 storage ring, which is performing the top-up operation, the high reliability of the linac has been advanced as follows: For reduction of phase variations caused by the waveguide deformation due to the variations of temperature or atmospheric pressure, the waveguide circuit of SF6 enclosure type, which fed RF powers to the bunching section, was replaced with that of vacuum type. And S-band 10MW circulators and isolators of vacuum type were adopted for the first time in the world. The timing system was improved so that the interval time of the beam injection into the 8GeV booster synchrotron and the 1.5 GeV NewSUBARU storage ring has been reduced to 1 sec from 15 seconds, respectively, even in the top-up operation of both storage rings. As a result, the stored current by the top-up operation were further stabilized. The stored current of the NewSUBARU storage ring was stabilized to 0.18% from 0.31%. The electron gun cathode assembly has been developed to reduce the dark emission from a grid plate by the double grid method and the electrolytic polishing.

MOPP123	Development Activities of Accelerator Instruments for SACLA	342
	Y. Otake, T. Asaka, T. Inagaki, C. Kondo, H. Maesaka, T. Ohshima, T. Sakurai, K. Togawa RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan H. Ego, S. Matsubara JASRI/SPring-8, Hyogo, Japan
	The X-ray free-electron laser, SACLA, is constantly operated for user experiments aimed at new science. Experimental users demand further experimental abilities, such as many experimental chances by using multi-X-ray beam lines, much better repeatability of the experiment conditions and further intense high-energy X-rays. To equip SACLA with these abilities in the future, we have developed a 2pi /3 CG acceleration structure with an acceleration gradient of over 45 MV/m to adapt operation for generating the intense high-energy X-rays. A high-voltage power supply to charge the PFN of a modulator, a klystron and an acceleration structure were developed to adapt operation for 120 pps operation from the present 30 pps, since 120 pps is more suitable for beam distribution to the multi-beam lines. To meet the experimental repeatability realized by stable timing in a pump-probe experiment, an optical-fiber length control system to mitigate timing drift below 1 fs for 10 minutes was developed. Highly precise cavity temperature control system in an injector for below ±2mK was also realized. Performances of our developed instruments were experimentally tested to be sufficient for our demands.

THPP119	Stabilization of Beam Performance due to Improvement of the Precise Temperature Regulation System of the SACLA Injector	1131
	T. Asaka, T. Hasegawa, H. Maesaka, Y. Otake, K. Togawa RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
	The temperature of rf cavities in the SACLA injector have to be precisely controlled to generate stable electron beam for XFEL users. To maintain the rf voltage and phase in the each cavity, the temperatures of all the cavities were kept within 28±0.04˚C by controlling the cooling water temperature. AC power supply of the controller to heat the cooling water was operated at 2Hz by PWM control with alternatively tuning on and off. The correlation between beam position variation and a leakage magnetic field due to applying the heater current of an AC power supply was found out. Although the cooling water temperature was controlled less than ±40mK, the laser intensity was affected by slight temperature drift. Therefore, thermometer modules were replaced to more precise ones with 1mK resolution. A new temperature regulation system using a continuous level control with DC power supply was installed. The fast fluctuation of the magnetic field leak by the heater current due to the PWM control was removed. Consequently, the beam position jitter in an undulator section was reduced to less than one-third and the laser position variation was suppressed within 20μm.

Paper

Title

Page

Storage Ring as a Linac Beam Monitor – Its Operation and Contribution to the Stable Top-up Injection

668

Y. Shoji
LASTI, Hyogo, Japan
T. Asaka, H. Dewa, H. Hanaki, T. Kobayashi, Y. Minagawa, A. Mizuno, T. Shinomoto, S. Suzuki, Y. Takemura, T. Taniuchi, K. Yanagida
JASRI/SPring-8, Hyogo-ken, Japan

We have used the electron storage ring, NewSUBARU, as a beam monitor of the SPring-8 linac. The time and transverse profiles of the injected linac beam are recorded in a frame of a dual-sweep streak camera. A measurements through synchrotron or betatron oscillation in the ring gives multi-dimensional beam structure. The system functions as a final check of the linac beam. It gives the time profile and energy profile or transverse emittance, which includes Twiss parameters. It measures parameters of one linac bunch in a long macro pulse. A shot-by-shot measurement gives beam fluctuations. We report how we use the system and its contribution to the stable top-up operation. The beam loading effect on the bunch energy was obtained by bunch-by-bunch energy profile measurements. It confirmed the optimization of the ECS (Energy Compression System) parameters. The single shot bunch-by-bunch vertical emittance measurement proved the difference between the front bunch and the following bunches. The same measurement showed a timing jitter of the electron gun pulse although the rf synchronization was perfect. This jittering had made the injection efficiency unstable.

MOPP093

Evaluation of Beam Energy Fluctuations Caused by Phase Noises

273

H. Hanaki, H. Dewa, S. Suzuki, K. Yanagida
JASRI/SPring-8, Hyogo-ken, Japan
T. Asaka, T. Ohshima
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

The SSB noises of the RF reference signal dominate the short-term instabilities of the RF phase of the carrier RF. This phase modulation finally results in beam energy fluctuation. This presentation gives a quantitative evaluation of the beam energy fluctuations in an electron linear accelerator caused by phase noises, comparing a theoretical analysis and experimental results. A simple model was introduced to understand how phase noises result in the relative phase difference between a beam bunch and accelerating RF fields. In the experiments, we measured the enhanced beam energy fluctuations by modulating the phase of the reference RF signals with an external signal. The interference between the accelerating RF phase modulation and the timing modulation of a beam bunch was found in the model analysis and also in the experimental results.

MOPP094

Latest Improvements of the SPring-8 Linac for High Reliability

276

S. Suzuki, H. Dewa, H. Hanaki, T. Kobayashi, T. Magome, A. Mizuno, T. Taniuchi, K. Yanagida
JASRI/SPring-8, Hyogo-ken, Japan
T. Asaka
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

In order to perform stable injection to the 8GeV SPring-8 storage ring, which is performing the top-up operation, the high reliability of the linac has been advanced as follows: For reduction of phase variations caused by the waveguide deformation due to the variations of temperature or atmospheric pressure, the waveguide circuit of SF6 enclosure type, which fed RF powers to the bunching section, was replaced with that of vacuum type. And S-band 10MW circulators and isolators of vacuum type were adopted for the first time in the world. The timing system was improved so that the interval time of the beam injection into the 8GeV booster synchrotron and the 1.5 GeV NewSUBARU storage ring has been reduced to 1 sec from 15 seconds, respectively, even in the top-up operation of both storage rings. As a result, the stored current by the top-up operation were further stabilized. The stored current of the NewSUBARU storage ring was stabilized to 0.18% from 0.31%. The electron gun cathode assembly has been developed to reduce the dark emission from a grid plate by the double grid method and the electrolytic polishing.

MOPP123

Development Activities of Accelerator Instruments for SACLA

342

Y. Otake, T. Asaka, T. Inagaki, C. Kondo, H. Maesaka, T. Ohshima, T. Sakurai, K. Togawa
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
H. Ego, S. Matsubara
JASRI/SPring-8, Hyogo, Japan

The X-ray free-electron laser, SACLA, is constantly operated for user experiments aimed at new science. Experimental users demand further experimental abilities, such as many experimental chances by using multi-X-ray beam lines, much better repeatability of the experiment conditions and further intense high-energy X-rays. To equip SACLA with these abilities in the future, we have developed a 2pi /3 CG acceleration structure with an acceleration gradient of over 45 MV/m to adapt operation for generating the intense high-energy X-rays. A high-voltage power supply to charge the PFN of a modulator, a klystron and an acceleration structure were developed to adapt operation for 120 pps operation from the present 30 pps, since 120 pps is more suitable for beam distribution to the multi-beam lines. To meet the experimental repeatability realized by stable timing in a pump-probe experiment, an optical-fiber length control system to mitigate timing drift below 1 fs for 10 minutes was developed. Highly precise cavity temperature control system in an injector for below ±2mK was also realized. Performances of our developed instruments were experimentally tested to be sufficient for our demands.

THPP119

Stabilization of Beam Performance due to Improvement of the Precise Temperature Regulation System of the SACLA Injector

1131

T. Asaka, T. Hasegawa, H. Maesaka, Y. Otake, K. Togawa
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

The temperature of rf cavities in the SACLA injector have to be precisely controlled to generate stable electron beam for XFEL users. To maintain the rf voltage and phase in the each cavity, the temperatures of all the cavities were kept within 28±0.04˚C by controlling the cooling water temperature. AC power supply of the controller to heat the cooling water was operated at 2Hz by PWM control with alternatively tuning on and off. The correlation between beam position variation and a leakage magnetic field due to applying the heater current of an AC power supply was found out. Although the cooling water temperature was controlled less than ±40mK, the laser intensity was affected by slight temperature drift. Therefore, thermometer modules were replaced to more precise ones with 1mK resolution. A new temperature regulation system using a continuous level control with DC power supply was installed. The fast fluctuation of the magnetic field leak by the heater current due to the PWM control was removed. Consequently, the beam position jitter in an undulator section was reduced to less than one-third and the laser position variation was suppressed within 20μm.