The Superconducting RF Photoinjector at ELBE

A superconducting RF photo-injector (SRF gun) has been installed at the ELBE linac. It is the first SRF gun which is in operation at an accelerator up to now. The SRF gun consists of a 3½ cell, 1.3 GHz superconducting cavity with normal conducting photocathode in it. At present, the gun delivers electron bunches with kinetic energies of 3 MeV in CW mode and up to 4 MeV in pulsed mode operation. The Cs2Te photo cathodes used in the gun exhibit a very long life time, e.g. a cathode was in use for more than one year and delivers a charge of 35 C. A degradation of the cavity performance due the normal conducting photo cathode was no found. The electron beam delivered to ELBE was used for beam transport optimization, longitudinal parameter and slice emittance measurements. The performance of the gun is mainly limited by the low gradient of the present cavity. For that reason two new and slightly modified cavities have been fabricated and tested at Jlab. The results of the vertical tests are very promising.