• G. Isoyama, S. Kashiwagi, R. Kato
  ISIR, Osaka
• H. Hayano, T. Muto, J. Urakawa
  KEK, Ibaraki
• M. Kuriki
  HU/AdSM, Higashi-Hiroshima

Funding: This research is partly supported by the accelerator support program to universities conducted by the High Energy Accelerator Research Organization in Japan.
We have begun a three-year project to develop a photocathode rf electron gun for the 40 MeV L-band linac at ISIR, Osaka University in collaboration with KEK. The L-band linac with an rf frequency of 1.3 GHz is equipped with a thermionic electron gun and it can accelerate a high-intensity single-bunch electron beam with charge up to 91 nC/bunch. Because the large emittance of ~100 pi mm x mrad is a limiting factor in the experiments, it is required to develop a new electron gun capable of providing an electron beam with much lower emittance. Since a group at the Accelerator Laboratory of KEK is developing a photocathode rf electron gun in the L-band for the International Linear Collider Project, we have joined the group to learn how to develop such an rf gun and also to obtain support from KEK. In this first year, characteristics of the rf gun will be measured at KEK for ILC fabricated by FNAL. We plan to optimize the structure of the rf gun for ISIR with computer simulation. We will report the plan and progress to develop a photocathode rf gun for the L-band linac.

• Y. Kato, A. Fujita, Y. Hama, T. Hirose, C. Igarashi, A. Masuda, A. Murata, T. Nomoto, K. Sakaue, T. Suzuki, M. Washio
  RISE, Tokyo
• H. Hayano, T. Takatomi, N. Terunuma, J. Urakawa
  KEK, Ibaraki
• Y. Kamiya
  University of Tokyo, Tokyo
• S. Kashiwagi
  ISIR, Osaka
• M. Kuriki
  HU/AdSM, Higashi-Hiroshima
• R. Kuroda
  AIST, Tsukuba, Ibaraki

Funding: Work supported by MEXT High Tech Research Project HRC707, JSPS Grant-in-Aid for Scientific Research (B)(2) 16340079
At Waseda University, we have been developing a high quality electron source based on photo-cathode rf gun which has a Cs-Te cathode with high quantum efficiency. Until now, at the Waseda University we have succeeded the soft X-ray generation via inverse-Compton scattering and pulse radiolysis system for studying the early processes of radiation chemistry with electron beams generated by copper cathode rf gun. Cs-Te rf gun is expected to generate higher charge electron bunches with a low emittance than a copper cathode because of its high quantum efficiency and also the high-quality multi-bunch electron beams. That enables us to extend the range of electron beam parameters for our application experiments. However, a Cs-Te cathode has a short life compared with a copper, so it has to be exchanged occasionally, thus we have developed a new rf-gun cavity which can be attached the compact cathode load-lock system. Moreover, we improved the design of an existing rf-gun cavity for the reduction of the dark current and the higher electric field. In this conference, the performance of the improved cavity and the result of electron beam generation experiments will be reported.

• G. Isoyama, S. Kashiwagi, R. Kato, M. Morio, S. Suemine
  ISIR, Osaka

Funding: This research is partly supported by the accelerator support program to universities conducted by the High Energy Accelerator Research Organization in Japan.
The 40 MeV L-band electron linac at the Institute of Scientific and Industrial Research, Osaka University is operated for joint-use in Osaka University. It is equipped with a three-stage sub-harmonic buncher (SHB) system consisting of two 108 MHz and a 216 MHz rf cavities to produce a high-intensity single-bunch beam. They were quarter-wavelength coaxial cavities made of a clad plate of copper on stainless steel and were inefficiently cooled with water flowing through a pipe wound on their outer surfaces made of stainless steel. We have renewed the cavities with new ones made only of oxygen-free copper to solve the problem. We made physical design and basic mechanical design of the new rf cavities by ourselves by taking a mechanical design of the SHB cavity of the electron-positron linac at KEK, Japan as a model. Special care was devoted in the mechanical design to cool the most part of the cavities directly with water instead of relying on heat conductivity in copper so that they are stable in regard to temperature. They have been installed in the linac and have been working well in expected performance. We will report details of design and fabrication of the new SHB cavities.