Status of the 3 1/2 Cell SRF Gun Project in Rossendorf

This paper describes the current status of the 3 1/2 cell SRF gun. The SRF photo injector will produce short pulses with high bunch charges and low transverse emittance like the traditional photo injector. The requirement for the ELBE superconducting electron linear accelerator is to provide low emittance electron beam with 1 mA current and 9.5 MeV energy. Additionally, it will easily operate in the CW-mode caused by the low RF power losses in the superconducting material. This is an exceptional property of the mid infrared ELBE-FEL to work in such a regime. Therefore, the normal conducting copper cathode must be cooled by liquid N2 in order to preserve the temperature of the cavity at 2 K. The estimated power input from the RF field into the cathode amounts 10 W. First results of temperature distributions on the cathode respectively the cooling system by a heat load of 10 W are presented.