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

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

3. 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

4. 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

5. 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

6. Magnetic hygiene
A new degaussing system (Maurer Magnetics DN 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

7. Vacuum pumps for FPC waveguides
Use NEG-SIP combination pumps (Saes Getters, NEXTORR D 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

8. 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

9. Questions?
Cryomodule design changes for C75

10. Backup slides
Cryomodule design changes for C75

11. 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 = 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

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

13. 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

14. 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