Konomi, T. Honda, Y. Kako, E. Kobayashi, Y. Michizono, S. Miyajima, T. Sakai, H. Umemori, K. Yamaguchi, S. Yamamoto, M. JACoW Publishing Geneva, Switzerland 2226-0366 978-3-95450-194-6 10.18429/JACoW-LINAC2018-TUPO074 English 510-512 TUPO074 cathode gun SRF cavity niobium Contribution to a conference proceedings 2019 2019-01 https://doi.org/10.18429/JACoW-LINAC2018-TUPO074 http://jacow.org/linac2018/papers/tupo074.pdf Superconducting RF gun can realize high acceleration voltage and high beam repetition. KEK has been developing the 1.3 GHz elliptical type 1.5 cell superconducting RF gun to investigate fundamental performance. A surface cleaning method and tools are developed by using KEK SRFGUN #1 and high surface peak gradient 75 MV/m was achieved without field emission. SRFGUN #2 which equips the helium jacket and can be operated with electron beam was designed based on the SRFGUN #1. It can be operated with transmit type photocathode which include superconducting transparent material. The cathode plug is cooled by thermal conducting from the 2 K helium jacket and photocathode will be kept around 2K to maintain superconductivity. Bulk niobium photocathode plug and substrate will used for the fundamental performance test. In parallel, the photocathode deposition chamber for multi-alkali photocathode will be prepared.