• C. Shonaka, H. Higaki, K. Ito, D. Kubo, M. Kuriki, H. Okamoto
  HU/AdSM, Higashi-Hiroshima
• T. Konomi, T. Nakanishi, S. Okumi, M. Yamamoto
  Nagoya University, Nagoya

High brightness electron source is a key technology for future projects based on advanced accelerators. Although GaAs photo-cathode is very attractive because it can generate highly polarized and extremely high brightness electron beam, the limited operational life time is a technical issue. In Hiroshima University, a photo-cathode test bench is implemented for various studies of GaAs photo-cathode. Super high vacuum, 9E-9Pa, was achieved and the cathode was successfully activated by processes of heat cleaning technique and the alternate evaporation of Cs and oxygen. The quantum efficiency and its lifetime were investigated as a function of cathode temperature, simulating temperature rise by the high power cathode drive laser. Wavelength dependence was also investigated.

• R. Hajima
  JAEA/FEL, Ibaraki-ken
• Y. Honda, T. Miyajima, T. Muto, M. Yamamoto
  KEK, Ibaraki
• H. Iijima, R. Nagai, N. Nishimori
  JAEA/ERL, Ibaraki
• M. Kuriki
  HU/AdSM, Higashi-Hiroshima
• T. Nakanishi, S. Okumi
  Nagoya University, Nagoya

A 500-kV, 10-mA photocathode DC gun has been designed and is now under fabrication by the collaboration efforts of JAEA, KEK, Hiroshima Univ. and Nagoya Univ. The Cockcroft-Walton generator and the ceramic insulator are installed upright in the SF6 tank. We have adopted a multiple-stacked cylindrical ceramic insulator, because this type of ceramic insulator has shown good stability and robustness at the 200-kV Nagoya polarized gun and the 250-kV JAEA FEL gun. All the vacuum chambers are made of titanium alloy with very low out-gassing. The Cockcroft-Walton generator, the ceramic insulator, the vacuum chambers will be fabricated by April 2009 and a high-voltage test will be started soon later. Up-to-date status of the gun development will be presented in detail.