• W. Singer, S. Aderhold, A. Brinkmann, R. Brinkmann, J.A. Dammann, J. Iversen, G. Kreps, L. Lilje, A. Matheisen, W.-D. Möller, D. Reschke, J. Schaffran, A. Schmidt, J.K. Sekutowicz, X. Singer, H. Weise
  DESY, Hamburg
• P.M. Michelato
  INFN/LASA, Segrate (MI)

The preparation phase for the European XFEL cavity production includes a number of actions. Material issues: qualification of high purity niobium vendors, verifying of large grain material as a possible option, construction of the scanning device for the niobium sheets. Mechanical fabrication issues: accommodation of the TESLA cavity design to the XFEL demands, device construction for RF measurement of components, integration of the helium tank and it's welding to the cavity into the fabrication sequence, documentation and data transfer, application of a new high resolution camera for inspection of the inside surface. Treatment and RF measurement: establishing the XFEL recipe, in particular the final surface treatment (final 40 μm EP or short 10 μm Flash BCP), and the cavity preparation strategy (vertical acceptance test with or without helium tank welded, with or without assembly of HOM antennas), construction of the cavity tuning machine. About 50 prototype cavities are produced at the industry, treated (partially in industry and partially at DESY) and RF-tested at DESY. The XFEL requirements are fulfilled with a yield of approx. 90%.

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