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Update on activities of investigations for analysis of module cavity degradation

Update on activities analyzing degradation in module cavities, potential sources, resonator statistics, logbook analysis, hardware inspections, RF test statuses, and conclusions from the TTC Meeting Beijing Dec. 2011.

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Update on activities of investigations for analysis of module cavity degradation

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  1. 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

  2. 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 ??

  3. 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

  4. Statistics of Degraded Cavities

  5. Position of degraded Cavities Statistic of position of resonators showing reduced performance in modules => Position 3 + 6: ??? Remark: Leak check during string assembly after P4

  6. Analysis of Logbooks for Z88, Z108, AC127, Z133 • StorageZ108; 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.

  7. Status of RF tests on degraded cavities

  8. Q(E)-measurements of Z88

  9. Q(E)-measurements of AC127

  10. 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

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