CEPC Cryogenic System Jianqin Zhang Shaopeng Li Accelerator

CEPC Cryogenic System Jianqin Zhang, Shaopeng Li Accelerator Divison, IHEP 2018. 06. 29

Outline n Introduction n Heat load n Refrigeration n Cooling scheme n Cryomodules n Cryogenics for magnets n R&D n Summary

Introduction n The Cryogenic system will cool all the cavities in a liquid-helium bath at a temperature of 2 K to achieve a good cavity quality factor. n The Cryogenic system lies besides the RF station, which provides helium for the collider ring and the booster ring. n The Cryogenic system mainly includes the refrigerators, distribution boxes, compressor group, helium storage tanks and cryomodules.

Introduction Booster ring: Ø 1. 3 GHz 9 -cell cavities, 96 cavities Ø 12 cryomodules Ø 3 cryomodules/each station Ø Temperature: 2 K/31 mbar Collider ring: Ø 650 MHz 2 -cell cavities, 240 cavities Ø 40 cryomodules Ø 10 cryomodules/each station Ø Temperature: 2 K/31 mbar

Flowchart of one Cryo-station • Each Cryo-station mainly includes Compressor, Cold box, helium gas storage tanks, cryomudules and purification system. • The cryomodules have two shields, a 40 K~80 K shield and a 5 K~8 K shield. • A 2. 2 K, 1. 2 bar helium is supplied for the cryomodules and the 2 K, 31 mbar helium gas return to the cold box with the cold compressors.

Infrastructure Each cryo-station has an underground plant in the gallery, the size is 37 m * 8 m.

Infrastructure

Infrastructure

Parameters of SC cavities related for Cryogenic system Collider 　mode Frequency(MHz) Cavity operating voltage (MV) Duty factor Total number of cavities Total number of modules Eacc (MV/m) R/Q Q 0 Operation temperature (K) Cavity dynamic heat load@ 2 K (W/cavity) Cavity dynamic heat load@ 2 K (W/module) Booster H W Z 650 650 1300 9. 04 0. 10 0. 90 19. 17 11. 72 12. 19 CW CW CW 0. 043 0. 029 0. 079 240 216 120 96 64 32 40 36 20 12 8 4 19. 66 9. 46 3. 62 19. 77 8. 81 8. 64 213 213 1036 1. 50 E+10 1 E+10 2 2 2 25. 59 5. 93 0. 87 1. 75 0. 23 0. 61 153. 52 35. 57 5. 22 13. 98 1. 87 4. 91

Heat load Higgs Mode Unit Collider 40 -80 K 5 -8 K 300 60 Booster 40 -80 K 5 -8 K 140 20 2 K 12 2 K 3 Predicted static heat load per cryomodule W Cavity dynamic heat load per cryomodule W 0 0 153. 59 0 0 13. 98 HOM dynamic heat load per cryomodule W 20 12 2 2 1 1 Input coupler dynamic heat load per cryomodule Module dynamic heat load Connection boxes Cryomodule number Total heat load Total predicted mass flow W 60 40 6 40 3 0. 4 W W 　 k. W 80 50 161. 59 10 42 50 7. 34 2. 78 4 10 12 0. 41 15. 38 10 17. 20 52 10 40 4. 88 g/s 82. 42 13. 34 12. 73 16. 07 Overall net cryogenic capacity multiplier 　 1. 54 4. 5 K equiv. heat load with multiplier k. W 1. 99 6. 80 36. 18 0. 32 0. 57 1. 68 Total 4. 5 K equiv. heat load with multiplier Total 4. 5 K equiv. heat load of booster and collider k. W 152. 26 346. 58 44. 96 2. 57 47. 53 0. 34

Heat load and installed power with different working modes 　 Collider H W Z Booster H W Z Total heat load @ 4. 5 K (k. W) 44. 96 19. 81 9. 24 2. 57 1. 51 1. 23 9. 84 4. 34 2. 02 0. 56 0. 33 0. 27 Total installed power (MW) H Total heat load @ 4. 5 K (k. W) Total installed power (MW) 47. 53 10. 40 W Z 21. 32 10. 47 4. 67 2. 29 • Four individual 18 k. W@4. 5 K refrigerators will be employed for the CEPC cryogenic system. • Referred to LHC 18 k. W refrigerator, the corresponding installed power is 16. 6 MW.

Helium Inventory • The volume of one 1. 3 GHz module and one 650 MHz module is about 320 liters and 346 liters, respectively. • The total liquid helium volume in the system will be 25, 257 liters. • To safely operate the cryogenic system, a coefficient factor 60% is added, so CEPC needs a standard 3. 8 E 4 m 3 helium inventory system.

Refrigeration • With a 35% margin, four individual 18 k. W@4. 5 K refrigerators will be employed. • The total cryogenic capacities are equivalent to 72 k. W at 4. 5 K. and 31 mbar 2 K gas helium

Cooling scheme

Cooling scheme for Collider

Cooling scheme for Booster

Cryomodule for 650 MHz 2 cell cavities From Ruixiong Han • Including six 2 -cell 650 MHz superconducting cavities, six high power couplers, six mechanical tuners and two HOM absorbers • Fast Cool-down is introduced, means 10 K/minute below 45 K. • The static heat load of whole cryomodule is 5 W at 2 K.

Cryomodule for 1. 3 GHz 9 -cell cavities Design Goals: • Low heat loss • Fast cool down XFEL / LCLS-II type Cryomodule for High Q Cavity • Cryogenic Group in IHEP has manufactured 58 1. 3 GHz 9 -cell Cryomodules for EXFEL cooperated with domestic companies. • It’s a good foundation for the optimization design for the CEPC cryomodules.

Cryogenics for SC magnets • 2 IPs in CEPC Interaction Region, there are 4 QD 0 magnets, 4 QF 1 magnets, 4 anti-solenoids and 32 sexupole magnets. • There are 2 cryo-stations, each one with a refrigerator of 3 k. W@4. 5 K. Refrigeration: 3 k. W@4. 5 K

R&D Large Helium Refrigerator Ø The refrigerator has the equivalent cooling capacity of 18 k. W at 4. 5 K. Ø Design work on the large helium refrigerator for CEPC will be carried out according to our demands. Ø There are five pressure levels in the cryoplant: 20 bara, 4 bara, 1. 05 bara, 0. 4 bara and 3 k. Pa. These are obtained with the high pressure screw compressor group, middle pressure screw compressor group, vacuum pumps and cold compressors.

R&D Cold compressor • Cold compressor is the key equipment for large 2 K cryogenic system (mass flow> 10 g/s). • Only a few core manufacturers abroad have the design and manufacturing capacity. The research of cold compressor is ongoing and supported by Key independent deployment project of Particle Accelerator Physics and Technology Key Laboratory. 4. 2 K Refrigerator Cold compressor Technical parameters: Ø Ø Ø adiabatic efficiency: ≥ 60% Compression ratio: ≥ 2 Leakage rate: 10 -9 Pa • m 3/s A high-speed motor output power: ≥ 1 k. W High speed motor speed: ≥ 36 krpm

R&D 2 K JT heat exchanger n The J-T heat exchanger is one of the key components of the 2 K cryogenic system. Key points： • efficiency ≥ 85% • Pressure drop ≤ 100 Pa • Low heat loss JT HX can increase the liquid quality by 30% at 2 K！ Shell and finned tube HX üThe 2 K JT heat exchangers(HXs) were designed, the flow is 2 g/s , 5 g/s and 10 g/s. ü 2 K JT HX test stand will be built in PAPS in 2018. üThe 2 K JT HX with high efficiency will be used in the CEPC cryogenic system.

Summary n The heat load is evaluated, the required total 4. 5 K equiv. heat load is 47. 53 k. W and total installed power is 10. 4 MW. n There are four cryo-stations and each station has an individual 18 k. W@4. 5 K refrigerator. n The R&D of 2 K JT heat exchanger and cold compressor is under way.