• A. Schmidt, G. Kreps, A. Matheisen, H. Weitkaemper
  DESY, Hamburg

Super conducting resonators are cooled by liquid helium. For the application in accelerator modules most superconducting resonators are equipped with individual helium containers. During the welding of the helium tank to the super conducting resonator special care has to be taken not to change the resonator specific data like acceleration gradient, resonance frequency and the cell to cell distribution of the accelerating field. At DESY a tank welding process and an in situ field profile control system on the basis of the bead pull field profile measurements (FMS) is set up. We report on the experiences and results of the welding procedures and the application of the FMS at DESY.

• B. van der Horst, A. Matheisen, B. Petersen, M. Schmoekel, N. Steinhau-Kuehl, H. Weitkaemper
  DESY, Hamburg

Within the last decade the production and preparation of superconducting resonators became more and more stable at DESY. Two cycles for the final surface preparation, the final surface removal by electro polishing (EP) and the final surface removal by a short buffered chemical polishing (BCP flash) are the baseline of cavity surface preparation at DESY. Basing on the positive development overtime and in view of industrialization of the processes for the XFEL project, a proposal for a reduced number of work steps was presented on the SRF 2007 workshop in Beijing [1]. Two parallel preparation lines, the final EP and BCP flash line, are tested on 15 cavities, for each line since. The cavities were produced by two different suppliers and randomly distributed to the preparation lines. In addition two industrial suppliers started industrialized electro polishing facilities for the main surface removal by electro polishing (main EP.) We present the cavity test results for the two preparation cycles.