Regular cryomodule maintenance plans (radiation damage, seals, etc) Michael Drury SRF Operations Support Jefferson Lab

Maintenance Plans - Reliability Complete C20 Warm Window Replacement Program Original cryomodules outfitted with polyethylene windows. Failure rate appeared to be increasing over the last year. Single window failure can take entire cryomodule out of service. Replace aging polyethylene windows with ceramics Five zones in SL completed Ten zones left with the bulk in the SL

Maintenance Plans - Reliability New hardware and procedures put in place to mitigate particulate / contaminant migration into cavities Upgraded portable clean room Slow bleed up pumping rig Helium Glove bag for window change out

Maintenance Plans - Reliability O-ring vacuum seal replacement program Insulating Vacuum seal Located in end cans at either end of cryomodule Failure of seal in 2L17 may be due to radiation damage Insulating Vacuum spoiled Higher heat load Tuners frozen Cryomodule mostly offline

Maintenance Plans - Reliability Root cause of failure at 2L17 not yet known May be radiation related ? May be age? Assume for now that 2L17 first of many Start replacing O-rings as we replace warm windows O-ring replacement involves beamline Potential for multiple module warm ups Take advantage of the current large population of warm modules?

Maintenance Plans - Reliability Beamline valve replacement Viton seals degrade in radiation environment Valves do not seal Not a crippling failure but complicates other tasks Forces multiple cryomodule warmups in order to access beamline

Maintenance Plans - Reliability Proposal: Find a manual all-metal valve that can be installed between girders and the B-pump drops. Reduce need for warming up cryomodules Could be installed between every cryomodule or between groups of cryomodules

Maintenance Plans - Reliability Real Time Repairs Insulating vacuum leaks Broken tuners Ion pump replacements Turbo Pump repair replacement

Maintenance Plans - Reliability Ongoing turbo pump repair and replacement Consider purchasing more of the Agilent Twistorr 304 style pumps Lower maintenance costs over time Lower capacity model may be acceptable (for cost saving) Need for LCW is a concern (air cooled model)

Other Support Energy Reach Complete the microphonics hardening installations Lead collar installations in C100 zones Support C50 / C75 Installations Includes installations and extractions Girder cleaning Commissioning Support investigations of in-situ degaussing Targeted Helium Processing Process Cryomodules that have lost ground Increased arc rates are one possible metric Further C100 Helium Processing Support SRFR&D efforts to understand cryomodule performance issues C50 Waveguide trips Field emission improvement efforts

Summary Current plans include Completion of warm window replacements Begin replacing O-ring seals in parallel with other maintenance and repair activities Support all Real Time Repair needs Support other Energy Reach enhancing activities While engaging in these activities: Utilize improved hardware and procedures to mitigate particulate contamination and migration Procure more Twistorr turbos Investigate an all metal valve installation