Cryomodule design modifications for C75 C75 implementation and project review G. Ciovati Saturday, December 29, 2018

Outline Tuner HOM stiffening brackets Magnetic shield and hygiene FPC waveguide vacuum FPC thermal intercept

Tuner The original tuner will be used Machining the profile of the cell holder clamps to fit new cell shape Replacement of some components (springs) with high remanent field J. Henry, G. Cheng, E. Daly Cryomodule design changes for C75

HOM stiffening brackets Supports were designed to restrain the HOM waveguides to tuner cell holder to increase the damping of mechanical mode of vibration close to 60 Hz (C50/C20 cavities also) G. Cheng, E. Daly, K. Davis, F. Fors, T. Powers, J. Henry Cryomodule design changes for C75

Magnetic shield A new magnetic shield (Cryoperm10, 1 mm thick) close to the cavity was designed to reduce the remanent H-field (a source of increased cavity RF heat load in CM) New magnetic shield G. Cheng, G. Ciovati, K. Macha, J. Henry Cryomodule design changes for C75

Magnetic hygiene A new degaussing system (Maurer Magnetics DN1100-1000 power module with CT2-U coil, 66 kA/m peak field, proprietary pulsing scheme) was procured for improved demagnetization of CM components G. Cheng, G. Ciovati Cryomodule design changes for C75

Vacuum pumps for FPC waveguides Use NEG-SIP combination pumps (Saes Getters, NEXTORR D200-5 ND, 200 liter/s pumping speed for H2), one for each FPC waveguide, to improve hydrogen pumping speed and reduce trip rate Implemented in C75 prototype cavity pair in 1L13 WG faults in 1L13 from 11/25/17 till 02/14/18 G. Ciovati, M. Stutzman, J. Fischer Cryomodule design changes for C75

FPC waveguide thermal intercept The width of the 50 K thermal intercept on the FPC waveguide is being optimized to accommodate up to 8 kW forward power (similar method used for FEL cryomodule) Realistic (thinner than nominal) thickness of Cu-plating has been considered and benchmarked with temperature profiles measured on a FPC waveguide installed in C50-12 Preliminary: extend intercept 1.5” closer to the cold flange. The estimated 2 K RF heat load is ~3 W at 8 kW forward power. F. Fors, G. Ciovati, F. Marhauser Cryomodule design changes for C75

Questions? Cryomodule design changes for C75

Backup slides Cryomodule design changes for C75

C50 cryomodules trips Courtesy: M. Drury WGVac WGV + Arc Arc Window Temp 1L04 427 97 6 1L05 84 17 3 1L06 591 62 12 1L11 22 4 1L12 249 98 121 114 2L04 415 206 92 74 2L07 14 42 2L09 36 2L10 276 127 5 2L15 41 58 45 2L16 49 15 2252 726 290 513 Courtesy: M. Drury WGVac Trips typically involve two cavities Data includes single events logged twice. Once for each cavity involved Removing duplicates gives slightly different picture 2252 WGVac trips over ~288 days of operation = 8 events / day across 87 cavities = 0.1 events / cavity / day Many events appear to occur at turn-on after trip / shut down or during a gradient increase Cryomodule design changes for C75

Waveguide vacuum trips: 1L04-1, 1L04-2 with RGA G. Ciovati, F. Humphrey, CEBAF operators Cryomodule design changes for C75

Current FPC waveguide pumping configuration three 90 bends ~23” long,  1-3/8” pipe Effective pumping speed of 20 l/s ion pump drops to ~10 l/s for H2 Pumping speed of cold window ~100 l/s for H2 Cryomodule design changes for C75

Magnetic field monitoring in C50-12 Increased residual field at the cavity after welding operations Residual field was unknown during cooldown because of faulty DAQ Q0 was highest in large grain C75 cavities Will evaluate addition of Cu-ring attached to vacuum vessel during welding and isolation of vacuum vessel “In-situ” degaussing of entire cryomodule will be evaluated starting April 2018 Cryomodule design changes for C75