Update on activities of investigations for analysis of module cavity degradation Degradation and possible sources Statistic of resonators Analysis of log books Analysis of hard ware Status of RF tests on degraded resonators Test results Conclusions Axel Matheisen, Denis Kostin, Detlef Reschke TTC Meeting Beijing Dec 2011

Degradation Degradation between last Q(E) in vertical acceptance test and module test => lot of handlings, treatment + assembly Degradation by a) enhanced field emission with lower usable / maximum gradient => typically explained by particle contamination during handling or improper venting condition b) reduced quench gradient => ??? In vertical acceptance tests degradation sometimes seen due to a) field emission activation during first power rise (Q(E)-curve) b) after quenches at high fields (>35 MV/m) by some MV/m (cure by warming-up => indication by one older single-cell test) c) after FE-processing ??

Handlings, treatments, assembly From vertical test to module test: - cleanroom assembly of power coupler - cleanroom connection of string - partially exchange of flanges (e.g. HOM feedthroughs) - HPR - partially tank welding (cavity stays closed) - several pumping and venting cycles

* Recruited for analysis Statistics of Degraded Cavities Module Cavity Pos Preparation Gradient drop Module Gradient (MV/m) 3* S32(X) 2 EP+BCP 8 19 3** Z102(X) 6 EP 9 22   AC116(X) 7 BCP flash 12 3*** AC118(X) 5 23 AC148(X) Z85 Z92 Z101(Y) 1 Z109 BCP+EP Z108(Y) 3 10 Z88(Y) 4 28 Z104 27 PXFEL1 Z100 13 PXFEL2 Z133 * 11 16 PXFEL3 Z88 * 18 AC127 * S1 global Z108* 20 CM1 Z89 17 AC73 15 (Y): Field emission loaded (X): No data of field emission available * Recruited for analysis

Position of degraded Cavities Position of Cavity in modules P1 P 2 P 3 P 4 P 5 P 6 P 7 P8 No of cavities degraded @ position 2 5 1 4 Statistic of position of resonators showing reduced performance in modules => Position 3 + 6: ??? Remark: Leak check during string assembly after P4

Analysis of Logbooks for Z88, Z108, AC127, Z133 Storage Z108; Z88; AC127: - non-standard storage (=> out of cleanroom) during cleanroom shut down (in respect to the other cavities of Module S1 global and PXFEL-modules) - stored closed under vacuum - cleaned manually (no US-cleaning due to assembled power coupler) Assembly procedures Z133; AC127; Z88: - No differences to other cavities in line found in assembly log book in respect of - particulates loading - assembly times - leakage found - RGA - Z108 ? People on place did not report on irregularities.

Analysis of hard ware Vacuum Z88 AC127 Z108 Accessories DESY Equipment Leak rate Z88 AC127 Z108 RGA OK P total before Module Accessories Power coupler cold part after dismounting Clean no sparks top no oxidation Wait for analysis HOM Antennas after dismounting OK no irregularity Flanges gaskets Ok no irregularity DESY Equipment Ultrasonic bath Non homogeneity top bottom; also in use for cavities not showing degradation Flange cleaning* manual cleaning due to installed power couplers for reentering cleanroom *New test set up developed not applied on these cavities yet

Status of RF tests on degraded cavities # Test mode Antenna type HOM installed AC127 gradient Eacc max (Fe onset ) Z88 gradient Eacc max (Fe onset ) Z133 gradient Eacc max (Fe onset ) 1 Vertical HQ No 27,6 (27) 30,4 (30) 27,3 (20,5) 2 Module PC Yes 19,2 (19) 18,5 (18) 16,2 (?) 3 CHECHIA 20,4 (19) 19,9 (18) ---- 4 ----- 12,8 (11)* 5 19,7 (14)   ----- 6 17,7 (13) Mode analysis HD ?? Remove tank 7 T map variable wait HQ = high Q antenna long pulse mode RF test PC = power coupler operated with Klystron in pulse mode Var= Variable antenna installed fro T map * Limitation by HOM coupler

Q(E)-measurements of Z88

Q(E)-measurements of AC127

Up to now: NO proveable explanation for degradation w/o FE Conclusion Up to now: NO proveable explanation for degradation w/o FE Vertical test with T-mapping and subsequent optical inspection of Z88, Z108 + AC127 in preparation