Photocathode RF gun using cartridge-type electric tubes

This report describes an S-band photoinjector with replaceable Cs2Te photocathodes. The photoinjector is equipped with a cathode-module, which is composed of four cartridge-type electric tubes with Cs2Te photocathodes. The photocathodes can be inserted into a single cell pillbox-type RF cavity. The maximum electric field strength on the photocathode surface, 90MV/m, has been achieved for the pillbox-type cavity in only 2h of RF processing following the exchange of the photocathode. The temporal behavior of the photocathode’s quantum efficiency was measured following application of the electric field strength of 90MV/m. The initial quantum efficiency of 3% was halved to 1.5% in 5h and finally settled to 1% after 15h. Analysis of the surface suggested the possibility of oxidization on the cathode surface rather than damage by vacuum discharges.