• 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.