Experience on In-Situ Module Repair and Set up of Non XFEL Cavity Strings at DESY

Abstract

All components installed to the European XFEL cavity string modules underwent an intensive inspection and quality control before acceptance for installation to cavities or modules. Even though some RF feed throughs for HOM coupler- and Pick Up antennas showed leaks at the ceramic insulation after module test at 2 K. Due to time restriction and continuity of production the exchange of these parts needed to be done without reentering the cleanroom. Successful repair of these modules took place by setting up a local cleanroom onto the cavity string.In collaboration with Helmholtz-Zentrum Dresden-Rossendorf (HZDR), a cavity string for the ELBE Project was assembled at DESY and transported to HZDR for installation to the vacuum vessel.A spare module with 3.9 GHz resonators for the Euro-pean XFEL was set up at DESY and will be tested and qualified for the European XFEL. Due to delay in delivery of the power couplers, four power couplers were installed after string assembly