Advances in large grain/single crystal SC resonators at DESY

Several single cell and three nine-cell large grain [LG] cavities of the TESLA shape have been fabricated and tested. The best accelerating gradient of Eacc= 41 MV/m was measured on an electropolished single cell cavity. All three nine-cell cavities fulfil the XFEL specification already in first RF test after BCP surface treatment. A fabrication method of single crystal cavities of an ILC like shape was proposed. A single cell single crystal [SC] cavity reached an accelerating gradient of 37.5 MV/m after BCP treatment only. The developed method can be extended on fabrication of multi cell SC cavities.