• I. Ito, N. Nakamura
  ISSP/SRL, Chiba
• Y. Honda
  KEK, Ibaraki
• Y. Kobayashi, K. Torizuka, D. Yoshitomi
  AIST, Tsukuba

We are developing an Yb fiber laser system that drives an ERL photocathode gun. An Yb fiber laser is expected to have both high stability and high output power required for the drive laser of an ERL photocathode gun. First we started to develop an Yb fiber laser oscillator with a high repetition rate up to 1.3 GHz that is the RF frequency of a superconducting accelerating cavity and then a 30W preamplifier using an Yb doped photonic crystal fiber. We report our recent progress in this development.

• N. Nakamura
  ISSP/SRL, Chiba
• R. Hajima
  JAEA/ERL, Ibaraki
• K. Harada, Y. Kobayashi, S. Sakanaka, M. Shimada
  KEK, Ibaraki

In ERLs, superconducting cavities accelerate low-emittance beams with high-gradient standing-wave RF fields. If alignment error of the cavities is considerable, they can harmfully affect the beam trajectory and quality because the cavities have strong transverse focusing. Achieving high alignment accuracy of the cavities is difficult compared with the other ERL elements such as magnets because the cavities are contained in cryomodules. Therefore we studied effects of the alignment error of main superconducting cavities with analytical approaches and simulations, using a one-loop model of the compact ERL as an example. In this paper, we present the effects of alignment error of main superconducting cavities on ERLs and their correction.

• N. Nakamura
  ISSP/SRL, Chiba
• R. Hajima
  JAEA/ERL, Ibaraki
• Y. Kobayashi, T. Miyajima, S. Sakanaka, M. Shimada
  KEK, Ibaraki

In ERL-based light sources, higher accuracy is expected to be required for RF control and timing, because the ERL beam has much shorter bunch length (less than 100 fs at minimum) compared with that of the existing SR sources. We studied effects of RF amplitude and phase variation of main superconducting cavities and effects of timing jitter of beam injection from an injector, using a simulation code 'elegant'. In this paper, we present the simulation results and discuss tolerances for the RF amplitude and phase and the injection timing.

• N. Nakamura
  ISSP/SRL, Chiba
• K. Harada
  KEK, Ibaraki

Orbit correction in an ERL is more complicated than those of an ordinary linac and a transport line, because the ERL beam passes a straight section containing main superconducting cavities at least two times with different energies. A corrector in this section gives a different kick angle to the beam in a different turn. Therefore a sophisticated orbit correction method is required for ERLs and ERL-based light sources. The eigenvector method with constraints (EVC)* can perform global orbit correction under constraint conditions and has been proposed and used for uniting global and exact local orbit corrections mainly in storage-ring based SR sources**. We applied this EVC method to orbit correction in an ERL. In this paper, we present how to use the EVC method for an ERL and simulation results of orbit correction for the compact ERL.

* N. Nakamura et al., Nucl. Instr. Meth. A 556 (2006) 421-432.
** K. Harada et al., Nucl. Instr. Meth. A 604 (2009) 481-488.

• H. Sakai, T. Furuya, S. Sakanaka, T. Takahashi, K. Umemori
  KEK, Ibaraki
• A. Ishii, N. Nakamura, K. Shinoe
  ISSP/SRL, Chiba
• M. Sawamura
  JAEA/ERL, Ibaraki

We started to develop an input power coupler for a 1.3GHz ERL superconducting cavity for ERL main linac. Required input power is about 20kW for the cavity acceleration field of 20MV/m and the beam current of 100mA in energy recovery operation. The input coupler is designed based on the STF-BL input coupler, especially choke-mode type ceramic window was applied. After that some modifications are applied for the CW 20kW power operation. We fabricated input coupler components such as ceramic windows and bellows and carried out the high-power test of the components by using a 30kW IOT power source and a test stand constructed.

• S. Sakanaka, M. Akemoto, T. Aoto, D.A. Arakawa, S. Asaoka, A. Enomoto, S. Fukuda, K. Furukawa, T. Furuya, K. Haga, K. Hara, K. Harada, T. Honda, Y. Honda, H. Honma, T. Honma, K. Hosoyama, M. Isawa, E. Kako, T. Kasuga, H. Katagiri, H. Kawata, Y. Kobayashi, Y. Kojima, T. Matsumoto, H. Matsushita, S. Michizono, T.M. Mitsuhashi, T. Miura, T. Miyajima, H. Miyauchi, S. Nagahashi, H. Nakai, H. Nakajima, E. Nakamura, K. Nakanishi, K. Nakao, T. Nogami, S. Noguchi, S. Nozawa, T. Obina, S. Ohsawa, T. Ozaki, C.O. Pak, H. Sakai, H. Sasaki, Y. Sato, K. Satoh, M. Satoh, T. Shidara, M. Shimada, T. Shioya, T. Shishido, T. Suwada, M. Tadano, T. Takahashi, R. Takai, T. Takenaka, Y. Tanimoto, M. Tobiyama, K. Tsuchiya, T. Uchiyama, A. Ueda, K. Umemori, K. Watanabe, M. Yamamoto, S. Yamamoto, Y. Yamamoto, Y. Yano, M. Yoshida
  KEK, Ibaraki
• M. Adachi, M. Katoh, H. Zen
  UVSOR, Okazaki
• R. Hajima, R. Nagai, N. Nishimori, M. Sawamura
  JAEA/ERL, Ibaraki
• H. Hanaki
  JASRI/SPring-8, Hyogo-ken
• H. Iijima, M. Kuriki
  HU/AdSM, Higashi-Hiroshima
• I. Ito, H. Kudoh, N. Nakamura, S. Shibuya, K. Shinoe, H. Takaki
  ISSP/SRL, Chiba
• H. Kurisu
  Yamaguchi University, Ube-Shi
• M. Kuwahara, T. Nakanishi, S. Okumi
  Nagoya University, Nagoya
• S. Matsuba
  Hiroshima University, Graduate School of Science, Higashi-Hiroshima
• T. Muto
  Tohoku University, School of Scinece, Sendai
• K. Torizuka, D. Yoshitomi
  AIST, Tsukuba

Future synchrotron light source using a 5-GeV-class energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting active R&D efforts for that. We are developing super-brilliant DC photocathode guns, two types of cryomodules for both injector and main superconducting linacs, 1.3 GHz high CW-power rf sources, and other important components. We are also constructing a compact ERL for demonstrating the recirculation of low-emittance, high-current beams using those key components. We present our recent progress in this project.