• T. Hasegawa, T. Inagaki, Y. Otake, T. Sakurai
  RIKEN/SPring-8, Hyogo
• S. Takahashi
  JASRI/SPring-8, Hyogo-ken

This paper describes the present status of a precise temperature-regulation system for the C-band accelerator at XFEL (X-ray Free Electron Laser)/SPring-8. It is essential to maintain a constant temperature of an rf cavity for stable lasing. We therefore installed a heater-assembly unit into a cooling water circuit of each rf cavity. By controlling the heater power, the temperature of the cavity can be stabilized. We constructed a prototype of this system at the SCSS (SPring-8 Compact SASE Source) test accelerator to check its feasibility for the XFEL. The prototype significantly contributes to a stable supply of SASE to users. For the XFEL, we simplified this system in consideration of cost and controllability. For example, to make one regulation system simultaneously controlling two C-band accelerating structures was tried. Keeping a temperature variation as tight as ±0.02 K at any operational mode could be achieved by this system. The preliminary test results of the system are also reported in this paper.

• T. Inagaki, N. Adumi, T. Hasegawa, H. Maesaka, S. Matsui, T. Sakurai, T. Shintake
  RIKEN/SPring-8, Hyogo
• H. Kimura, C. Kondo, K. Shirasawa
  JASRI/SPring-8, Hyogo-ken

C-band (5712 MHz) accelerator is used as the main accelerator of the XFEL in SPring-8. Since the C-band generates a high accelerator gradient, as high as 35 MV/m, the total length of the 8-GeV accelerator fits within 400 m, including the injector and three bunch compressors. We use 64 C-band rf units, which consists of 128 accelerating structures, 64 rf pulse compressors, 64 klystrons, waveguide components, etc. Mass-production of these high power rf components has been almost completed. Production quality is confirmed by the high power rf test. Installation of the C-band components started in August 2009. So far, about half of the components have been installed on schedule. The accelerating structures are aligned with about 0.1 mm accuracy. By the date of the IPAC'10 conference, we will almost complete the installation. In this presentation, we will report the construction status.