Status of the 3 1/2 Cell Rossendorf Superconducting RF Gun

In Rossendorf it was shown for the first time that a RF electron gun where a photo cathode is inside a superconducting cavity, works stable over a period of seven weeks. At 4.2K no change of the quality factor Q = 2.5 10⁸ has been observed [1]. The experimental results were the basis for the design of a new 3.4 cell superconducting RF photo electron gun [2]. The paper presents details of different components of this gun, explains the status of manufacturing and gives results of first test measurements. Furthermore, the idea is discussed to use for emittance compensation instead of a static magnetic field which is inside the cavity of a normal conducting RF gun in the superconducting gun cavity an additional magnetic RF field (TE₀₁₁ mode) . By computer simulation the attraction of this idea is demonstrated.