Cs2Te and metallic photocathodes for SRF gun at HZDR

Quality of photocathode is one of the critical issues for the stability and reliability of the photoinjector system. SRF Gun II with Mg photocathode has successfully provided stable electron beams for ELBE users at HZDR. In this work, we present the various cleaning processes (activation) for Mg photocathodes, e.g. high intensity laser cleaning and thermal treatment. Furthermore, we show the first result of the photoemission study on the alternative metallic cathode, for instance MgY alloy.

To generate higher bunch charge up to 0.5nC, Cs2Te photocathode is planned for SRF gun II. Up to now three Cs2Te photocathodes have been used in SRF gun II, however, they show abnormal phenomena and unwanted contamination for the superconducting cavity.