• W. Singer, S. Aderhold, J. Iversen, G. Kreps, L. Lilje, A. Matheisen, X. Singer, H. Weise
  DESY, Hamburg
• M. Pekeler, J.Sch. Schwellenbach
  ACCEL, Bergisch Gladbach
• F. Schoelz, B. Spaniol, E. Stiedl
  W.C. Heraeus GmbH, Materials Technology Dept., Hanau

A test program of 1.3 GHz TESLA shape 9-cell large grain (LG) resonators for the European XFEL project was started at DESY. The main aim is to find out whether or not the choice of LG material could be an option for the fabrication of approx. 800 XFEL resonators. Several aspects are under investigation and will be compared with the conventional polycrystalline material option. One of the aspects is the material issue: could the required amount of LG niobium be produced at industry in a cost effective and reliable manner? The second issue is the fabrication of cavities: could the series production of resonators be done on the level of required accuracy and costs? The third one is the performance issue: what is the appropriate treatment for reproducibly achieving the specified XFEL accelerating gradients? Development of the LG disc production was done within the framework of the R&D program of DESY and W. C. HERAEUS. Eleven resonators are produced at the company ACCEL. Up to now three resonators are RF-tested vertically. The He-vessel was welded onto one of the resonators which passed the horizontal RF-test. The data and perspectives of the LG cavity application are discussed.