Development of a Cs-Te cathode RF gun at waseda university

A photo-cathode RF-Gun is one of the good alternatives for the electron source, because of its high gradient on the electron emitter causing small beam emittance, and tenability of initial beam profile especially for electron bunch length. Therefore, we are operating as a high brigh-tness short pulse electron source. In last year, we have been developing a high quality electron source based on photo-cathode RF-gun which is newly designed RF cavity and has a Cs-Te cathode with high quantum efficiency [1] [2]. Improved RF-Gun cavity has four compact tuners on each half cell and full cell, which can be tuned the resonance frequency to deform the cavity wall. Also removing the Helicoflex seal and tuning holes, reduction of the dark current is expected. According to these improvements, the Q value and shunt impedance of the new RF-Gun cavity increased 20% compared with the previous RF cavity. In addition, the dark current of cavity was reduced and the good electron beam parameters could be achieved compared with pre-vious RF-Gun with a Cu cathode.