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, 90 MV/m, has been achieved for the pillbox-type cavity in only 2 h 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 90 MV/m. The initial quantum efficiency of 3% was halved to 1.5% in 5 h and finally settled to 1% after 15 h. Analysis of the surface suggested the possibility of oxidization on the cathode surface rather than damage by vacuum discharges.