W. Singer. SRF2011, July 25 ‐ 29, 2011, Chicago, Illinois, U.S.A. XFEL Cavity Recipe for Mechanical Fabrication and Treatment Waldemar Singer/DESY

W. Singer. SRF2011, Hot Topic. July 28, 2011, Chicago, Illinois, U.S.A. XFEL Specification: SERIES MECHANICAL FABRICATION: (XFEL/001- XFEL/018) SERIES SURFACE AND ACCEPTANCE TEST PREPARATION (XFEL/A - D) HARDWARE AND PROCESSES USED AT DESY (XFEL/Appendix I - IV) ILC-HI GRADE CAVITIES AS A TOOL OF QUALITY CONTROL (XFEL/HiGrade) SETS OF DRAWINGS Two main aims have been pursued: -Spec. has to contain all detailed recipes for the cavity mechanical fabrication, treatment and assembly for RF test -DESY experienced has to be included. The work was done by DESY experts and the assistance of the experienced external advisers from the industry. XFEL recipes are defined in XFEL Specification Specification is released. Contact person:

W. Singer. SRF2011, July 25 ‐ 29, 2011, Chicago, Illinois, U.S.A. 3 Some changes occurred as a result of negotiations with cavity producers. In particular DESY has taken over: Material procurement Performance guaranty Organization and costs for PED issues He-vessels fabrication for one of the companies Cavity transport containers and transport conditions are changed These changes forced us to adopt the specification documents to the order circumstances. -Change reports linked to companies have been created. In addition companies asked for approval of some changes in the specifications - Change requests and specification changes in some positions appeared Specification has to be agreed with vendors

W. Singer. SRF2011, Hot Topic. July 28, 2011, Chicago, Illinois, U.S.A. 4 Specified only critical for performance aspects. Some aspects of recipes are not specified by XFEL CVs Give to the companies as much as possible freedom in details

W. Singer. SRF2011, Hot Topic. July 28, 2011, Chicago, Illinois, U.S.A. - About 30 years of industrial fabrication of welded cavities - Main principle of fabrication is to do the best on all fabrication steps - Do we really know what fabrication aspects are critical (relevant) for the accelerating gradient? Some remarks to recipes possibly for discussion  Is grain size relevant? LG cavities as example (Eacc up to 45 MV/m)  Can the texture influence the performance?  Is the time between final etching of the part and EB welding (storage time) critical? Common requirement: the storage time has to be less than 8 hours. DESY: 1 week storage under vacuum is OK. 1 week storage under nitrogen atmosphere is OK  Recipe for repairing of burned holes?

W. Singer. SRF2011, Hot Topic. July 28, 2011, Chicago, Illinois, U.S.A. CV Horiz. Position. EBW: butt joint (E. ZANON,) CV Horiz. Pos. EBW: lap joint (recess) DESY, E.Zanon E-beam Cavity (CV) horizontal or vertical position? Lap (recess) or butt joint? CV Vert. Pos. EBW: lap joint (recess) e.g. RI, CERCA,

W. Singer. SRF2011, Hot Topic. July 28, 2011, Chicago, Illinois, U.S.A. Xenia Singer How smooth should be the equator weld?? Comparison of single cell programs (KEK and DESY) has shown that Eacc of CBP (centrifugal barrel polished) cavities is ca. 7% higher. CBP makes smoother mostly the equator weld area

W. Singer. SRF2011, Hot Topic. July 28, 2011, Chicago, Illinois, U.S.A. 8 DESY

W. Singer. SRF2011, July 25 ‐ 29, 2011, Chicago, Illinois, U.S.A. The R&D Process for TT: XFEL treatment recipe was worked out on base of prototype cavities Prior surface treatment. EP μm (main EP), ethanol rinse, outside BCP, 800°C annealing, tuning Final surface treatment - two alternative options 1. Final EP of 40 μm, ethanol rinse, high pressure water rinsing (HPR) and 120°C bake 2. Final BCP of 10 μm (BCP Flash), HPR and 120°C bake. Integration of the helium tank, assembly of HOM, pick up and high Q antennas before vertical RF test

W. Singer. SRF2011, Hot Topic. July 28, 2011, Chicago, Illinois, U.S.A. 10 Thank you