• H. Hanaki, T. Asaka, H. Ego, H. Kimura, T. Kobayashi, S. Suzuki, M. Yamaga
  JASRI/SPring-8, Hyogo-ken
• T. Fukui, T. Inagaki, N. Kumagai, Y. Otake, T. Shintake, K. Togawa
  RIKEN/SPring-8, Hyogo

The injector of the 8 GeV linac generates an electron beam of 1 nC, accelerates it up to 30 MeV, and compresses its bunch length down to 20 ps. Even slight RF instability in its multi-stage bunching section fluctuates the bunch width and the peak current of an electron beam and it accordingly results in unstable laser oscillation in the undulator section. The acceptable instabilities of the RF fields in the cavities, which permit 10% rms variation of the peak beam current, are only about 0.01% rms in amplitude and 120 fs rms in phase according to beam simulation. The long-term RF variations can be compensated by feedback control of the RF amplitude and phase, the short-term or pulse-to-pulse variations, however, have to be reduced as much as possible by improving RF equipment such as amplifiers. Thus we have carefully designed and manufactured the RF cavities, amplifiers and control systems, giving the highest priority to the stabilization of the short-term variations. Components of the injector will be completed by the end of the April 2010, and the injector will be perfected in the summer 2010. We will present the performance of the completed devices in the conference.

• T. Asaka, H. Ego, H. Hanaki, T. Kobayashi, S. Suzuki
  JASRI/SPring-8, Hyogo-ken
• T. Inagaki, Y. Otake, K. Togawa
  RIKEN/SPring-8, Hyogo

XFEL/SPring-8 is under construction, which is aiming at generating coherent, high brilliance, ultra-short femto-second X-ray pulse at wavelength of 1Å or shorter. The injector consists of a 500kV thermionic gun (CeB6), a beam deflecting system, multi-stage RF structures and ten magnetic lenses. The multi-stage RF structures (238MHz, 476MHz, 1428MHz) are used for bunching and accelerating the beam gradually to maintain the initial beam emittance. In addition, in order to realize linearizing the energy chirp of the beam bunch at three magnetic bunch compression systems after the injector system, we prepared extra RF structures of 1428MHz and 5712MHz. It is important to stabilize the gap voltage of those RF structures because the intensity of X-ray pulse is more sensitive for a slight variation of the RF system in the injector. We developed some stable amplifiers for those RF structures, and confirmed the amplitude and phase stability of an RF signal outputted from the amplifiers. The measurement results achieved nearly the requirement of design parameters. In this paper, we describe the development status and the achieved performances of RF equipment of the injector section.

• J. Watanabe, S. Kimura, K. Sato
  Toshiba, Yokohama
• T. Asaka, H. Ego, H. Hanaki
  JASRI/SPring-8, Hyogo-ken

TOSHIBA is manufacturing the L-band acceleration system for the SPring-8 Joint Project for XFEL. We have developed a new type duct-shaped SiC dummy load for its power distribution system. The load terminates a WR650 waveguide and can absorb the maximum mean power of 10kW. In order to reduce VSWR less than 1.1 in the frequency range of 1.428GHz, we shaped the SiC absorber into a 35cm long tapered cylinder and mounted matching stubs in the waveguide near the inlet of the load. The SiC absorber was fit into a cylindrical copper with efficient water-cooling channels. The design and manufacture and the low-power tests of our original dummy load are described in this paper.