• A. Brinkmann, M. Lengkeit, W. Singer, X. Singer
  DESY, Hamburg

For the XFEL cavity production a rather large quantity of niobium sheets from partially new niobium vendors has to be delivered according to the XFEL Cavity Specification. It is of high importance that the material monitoring of this niobium has to be done within the production process to ensure a high performance of the cavities. The quality assurance program includes electrical measurements, mechanical, structural and chemical material analysis. For the surface investigations two eddy current scanning devices have been fabricated on the basis of our specification and experience. The scanning process and evaluation of test result can now be done in a few minutes per sheet. We describe the material test methods and the scanning machine. Measured results of the pre-series niobium will be compared to older material tests results.

• J. Iversen, R. Bandelmann, G. Kreps, W.-D. Möller, D. Proch, J.K. Sekutowicz, W. Singer
  DESY, Hamburg

Since 1993 DESY ordered 165 1.3GHz 9-cell superconducting cavities. The cavities have been developed for TeV-Energy Superconducting Linear Accelerator (TESLA) and are used in the linac of the Free Electron Laser in Hamburg (FLASH). The fabrication of all cavities was done in 9 production groups at industry. From the beginning the industrialization was carried out in close collaboration between DESY and the industry. From order to order the cavity design was optimized and the fabrication sequences were improved to realize stable and better cavity performance and to safe costs. Now a final cavity design for the European XFEL is defined. We summarize the development phases and design changes up to the final XFEL design. An outlook on the near future production of hundreds of cavities for XFEL based on our experience will be given.