First beam commissioning of the HZB SRF photoelectron gun

The versatile 1.3 GHz superconducting radio-frequency (SRF) gun at HZB succesfully generated first photoemission beam from a high quantum efficiency (QE) multi-alkali photocathode. This demonstrates worldwide first beam operation of a SRF gun at high repetition rate and with a robust multi-alkali Na-based photoemissionn source. The setup of the test and all sub-systems is described. The latest results of SRF commissioning, cavity performance, photocathode QE measurements and beam parameter exploration campaigns is presented in the paper.