LINAC2014 - List of Authors (Otake, Y.)

Paper	Title	Page
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

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.