Solenoid magnet design for CEPC detector magnet Ning

Solenoid magnet design for CEPC detector magnet Ning Feipeng For the CEPC Detector Magnet Team 2019 -11 -20

Outline • 1, New yoke design of CEPC detector magnet. • 2, Cable development and Coil winding process. • 3, Cryogenic system. • 4, HTS plan for detector magnet. • 5, Conclusion.

1, New Yoke design • Comparison CDR original version New version CMS Central field (T) 4 Operating current (A) 19600 Inner diameter of coil 6360 (mm) Length of coil (mm) 12480 Barrel yoke inner 9180 diameter (mm) Barrel yoke outer 14000 diameter (mm) Total length of yoke 20040 (mm) Weight of barrel yoke (t) 6000 Weight of each end cap 2000 (t) Total weight of yoke (t) 10, 000 CEPC original 3 15779 7200 CEPC New version 3 16796 7200 7606 8800 7600 9200 14480 12120 13966 12020 5940 3316. 6 3137 1144 12, 573 5, 425

1, New Yoke design There are some equipment on the top of the barrel yoke, such as vacuum pump. So the magnetic field on the top of the barrel yoke must be controlled. CMS CEPC new Version

Stray field comparison Magnetic field strength at Booster (radial R=25 m) Stray field 50 Gs R direction Z direction 100 R Gs direction CEPC New original Version 25. 2 m 13. 6 m 20. 6 m CMS 32 m 19. 2 m 15. 8 m 25. 5 m 10 m 16. 4 m Z direction 25. 2 m 11. 6 m 20. 1 m Original version 8. 4 Gs New version 28 Gs

3 D yoke calculation • 1/24 model（dodecagon shape yoke） 1/24 model Axial magnetic field strength from 0 to 10 m, The results of 2 D are consistent with 3 D. 6

3 D Yoke force calculation • dodecagon yoke • The magnetic force of each piece of end yoke: Yoke number 1 2 3 4 5 6 Radial direction (t) 57. 8 17. 3 6. 5 5 3. 7 7 Axial direction (t) 138 67. 3 55. 5 44. 4 71. 3 260 2 D and 3 D Comparison of each layer of end yoke: Yoke number 1 2 3 4 5 6 2 D（t） 3230 1702 835 686 546 865 3 D*24（t） 3118 1656 807 666 533 856 7

3 D Yoke force calculation • The magnetic force of each piece of barrel yoke: 5 4 3 2 1 Radial direction (t) 1 2 3 4 5 113 42. 2 25. 6 15 35. 7 • If the barrel yokes are separated into two pieces, there is opposite magnetic force on the center support structure, the force (unit, t)： 5 4 3 2 1 1 2 3 4 5 61. 8 42 39. 2 36. 7 62. 1 8

Different Yoke design 12573 t 2874. 5 t 5425 t 1927 t 4036 t 1407 t 4980 t

2, Cable development and Coil winding process • Al Stabilized Rutherford cable development Cooperate with Toly company • Nb. Ti Rutherford cable meets the requirement. Nb. Ti Rutherford cable After warping, RRR value decreased by about Nb. Ti Rutherford cable After warping, Ic drops < 7%

2, Cable development and Coil winding process • Al Stabilized process: short sample ( 100 m) meets the requirements. Now is developing the long cable. ( 1 km)

2, Cable development and Coil winding process • We are seeking for cooperation. Two companies have been discussing, Xinli and Fubin. BES III CMS BABAR-1 BABAR-2

3, Cryogenic system Research on thermosiphon cooling system of small superconducting magnet This project is a preliminary study of CEPC, study thermosiphon cooling system Parameters of small magnet： • The largest magnetic field： 5. 64 T • Energy storage： 62. 62 KJ • Inductance： 19. 57 H • Running current： 80 A • Room temperature aperture： 80 mm • The length of the coil： 203 mm • The total number of turns： 14560 Physical diagram of small magnet

3, Cryogenic system Internal section size(mm) Wall thickness(mm) Length( mm) Cooltube Φ 8 1 400 Feed pipe Φ 12 2 600 Exhaust pipe Φ 12 2 140 The phase separator Φ 100 the upper plate 6，the bottom palte 10，cylinder 6 106 Steam tank、 Sump 50× 20 2 203 Exhaust pipe The phase separetor Steam tank Coil skeleton Cool tube Feed pipe Sump Schematic diagram of thermosiphon pipeline According to preliminary exploration , the whole thermosiphon circut performs better when the liquid level in the phase separator is around 50%. the requirement of the liquid helium is around 0. 35 L.

3, Cryogenic system G-M refrigerator Service tower The phase serpature Outer cylinder @300 K Cold shield @40 K Coil skeleton The simulation is finished, and get some results. Next is the preparation for the experiment. Small magnet thermosiphon experimental device

4, HTS plan for CEPC detector magnet HTS tape Radiation length: Material Thickness Radiation thickness Material Cu Fe Ag YBa 2 Cu 3 O 7 Mg. O Al 2 O 3 Ce. O 2 Total, Xtot X, mm 0. 01 0. 05 0. 002 0. 00000001 0. 00000008 0. 0000003 　 X 0, mm 14. 36 17. 57 8. 543 20 78. 28 70. 38 16. 54 　 Ratio 17. 97% 73. 41% 6. 04% 2. 58% 0. 00% 100% X/X 0 0. 0007 0. 0028 0. 0002 0. 0001 0. 0000 0. 0039 Radiation length Single tape 10 mm width 0. 0039 Stack Cable 30 layers 0. 117 10 mm Al stabilizer 0. 1125 Al stabilized HTS cable 0. 2357

4, HTS plan for CEPC detector magnet • Get the support form CAS to develop the HTS cable and prototype coil. • 1, Develop Re. BCO cable. Al Stabilized Re. BCO stacked Tape Cable (ASTC) TSTC(Twisted Stacked Tape Cable) by MIT 1, HTS stack cable CORC(Conductor On Round Core) by ACT RACC(Roebel Assembled Coated Conductor) by KIT ASTC(Al Stabilized HTS stacked Tape Conductor) by IHEP 2, Add Al stabilization to HTS stack cable 20 layers ASTC

4, HTS plan for CEPC detector magnet • 2, Develop the prototype of large HTS magnet. • study the winding process, cable joint, less material support structure, cooling system, quench protection and so on. Inner diameter 2 m Stack cable 4 mm width 20 layers Cable length 200 m Operating temperature 4. 2 K Current 6000 A

Conclusion • New Yoke version has been designed • Low temperature cable is developing on time. Seeking for cooperation on large coil winding process. • The prototype of cryogenic system is developing. • Gets funds for the prototype development of HTS plan, and is developing HTS cable.