Recent Cavity VT results at DESY Detlef Reschke

Recent Cavity VT results at DESY Detlef Reschke, Sebastian Aderhold TTC meeting, Milano, Feb. 28 – Mar 04

Outline n In general few vertical tests due to preparation of European XFEL series production Results of 8 Large Grain Cavities of PXFEL 3 n TTC Meeting Milano Feb 28 - Mar 04, 2011 Detlef Reschke, DESY 2

Large Grain Cavities AC 151 – AC 158 n n n n 3 8 LG-Cavities made from Heraeus Nb by RI/Accel First tests after pure BCP removal of 120 – 130 µm, HPR and 125 C, 48 h bake 7 of 8 cavities with 25 – 28 MV/m limited by BD, with no or low FE 3 cavities required add. HPR + 2 nd test due to FE in 1 st test 2 cavities: Quench location found with second sound => optical inspection without obvious defect 8 th cavity (AC 158) showed vacuum leaks and FE in 2 tests (28 MV/m) Next: EP of all cavities TTC Meeting Milano Feb 28 - Mar 04, 2011 Detlef Reschke, DESY

Cavities of PXFEL 3 4 Results of PXFEL 3 see talk of Denis Kostin n 2 of 8 cavities degraded seriously compared to vertical test before string assembly n 6 “good” cavities vertically re-tested (4 w + 2 w/o add. HPR) => performance more or less kept ( 1 cavity with stronger FE) => will be re-used for new assembly of “PXFEL 3_1” at Saclay n 2 “new” cavities with usable gradient of 25 -30 MV/m (Z 138, AC 147) n n Investigation of “bad” cavities ongoing (horizontal test, assembly + disassembly procedures, …) TTC Meeting Milano Feb 28 - Mar 04, 2011 Detlef Reschke, DESY