1. R&D Progress of the High Field Magnet Technology for CEPC-SPPC Qingjin XU On behalf of the SppC magnet working group Institute of High Energy Physics (IHEP) Chinese Academy of Sciences (CAS) 2015.9.11

2. a)Magnetic design study of the 20-T dipole b)Mechanical design study of the 20-T dipole c)Fabrication of high J c Nb 3 Sn wires (WST) d)Development of cabling machine (Toly Electric) e)Development of coil winding machine (SSTC) f)Practice of coil fabrication procedures g)Quench protection for 20-T magnets h)ICFA Mini-workshop

3. Number of apertures(-)2 Aperture diameter(mm)50 Inter-aperture spacing(mm)330 Operating current(A)14700 Operating temperature(K)1.9 Operating field(T)20 Peak field(T)20.4 Margin along the loadline(%)~20 Stored magnetic energy(MJ/m)7.8 Inductance (magnet)(mH/m)72.1 Yoke ID(mm)260 Yoke OD(mm)800 Weight per unit length(kg/m)3200 Energy density (coil volume)(MJ/m 3 )738 Winding pack current density(A/mm 2 )400 Force per aperture – X/Y(MN/m)23.4/2.4 Peak stress in coil(MPa)240 Fringe Field @ r = 750 mm(T)0.02 Magnetic design study of a 20-T dipole 20-T Nb 3 Sn + HTS common coil dipole for SppC Space for beam pipes: 2 * Φ50 mm; load line ratio: ~80% @ 1.9 K; yoke diameter: 800 mm Nb 3 Sn HTS Nb 3 Sn HTS Iron With 10 -4 field quality @ 2/3 aperture Main Design Parameters

4. Magnetic design study of a 20-T dipole Integrated multiples with optimized coil ends 20-T coil end design with common coil configuration Integrated bn/anValue (10 -4 ) b30.14 b51.42 b7-0.40 a2-0.29 a4-1.81 a60.03 Beam pipes: 2 * Φ50 mm Load line ratio: ~80% @ 1.9 K Yoke diameter: 800 mm

5. Chengtao Wang Different coil configurations for 20-T dipole Left: Common coil Right: Cos-theta Common coil Cos-theta Coil ends Common coilCos-theta Magnetic design study of a 20-T dipole

6. Yoke V-pad V-key Iron Bi2212 + Nb 3 Sn Coils h-pad h-key Beam support AL shell Total lorentz force per aperture: Fmag_x=23.4 MN/m Fmag_y=2.38 MN/m Stress in coil after excitation Stress in shell after excitation Mechanical design study of a 20-T dipole Kai Zhang

7. Mechanical design study of a 20-T dipole Kai Zhang et al. AL 7075 Yoke H-pad V-pad Dummy coil (Aluminum bronze) Cross section of a Nb 3 Sn Subscale magnet “Copper” Rutherford cable (32 strands, φ1.06 mm, 16.5mm x 2 mm) Test the yield strength of AL 7075 and other promising alum- inium alloys by applying the preload with water pressurized bladder and by cooling down. Test whether the AL shell can restore its original shape after unloading. Strain indicator

8. Fabrication of high J c Nb 3 Sn wires (WST) High J c Nb 3 Sn development at WST ~ Non-Cu J c > 2500 A/mm 2 @ 12 T, 4.2 K ! cross-section of the wire Internal-Tin process Available by Oct. 2015!

9. Development of Rutherford cabling machine (Toly) Advantages of the Rutherford cable Reduction of the strand piece length; Reduction of the coil inductance; Current redistribution in case of a defect in one strand; Twisted strands to reduce interstrand coupling losses and field distortions, and provide more mechanical stability. E.Todesco et al,USPAS,Superconducting Accelerator Magnets,January 23-27,2012 24 Ф0.727 NbTi strands with/without Sn coating Cabling machine at Toly Electric

10. Development of coil winding machine (SSTC) 收料盘张力传感放料盘 由三部分组成 : 收料盘、张力传感装 置及放料盘组成，各有福马轮可移 动、可固定。收料盘与放料盘的功 能可互换，可正反转，调速范围 0- 10rpm 。张力传感系统和放料盘高度 可调（ 900-1300mm ）；系统运行角 度 -45 度至 90 度可调。

11. Practice of coil fabrication procedures Kai Zhang, Chengtao Wang, Yinan Hu, Ershuai Kong, Guangdong Li et al.

12. Practice of coil fabrication procedures Kai Zhang, Chengtao Wang, Yinan Hu, Ershuai Kong, Guangdong Li et al.

13. Running current 93A 13 Quench Area Bz Operating Current 70A Coupling-loss Protection thermal disturbance electrical disturbance completely quench point Yinan Hu et al. Quench protection for high field magnets

14. All slides are available online: http://indico.ihep.ac.cn/event/4900/timetable/#all.detailed

15. Next steps  Conceptual Design study of the 20-T SPPC magnets (CEPC-SPPC CDR by end of 2016?) Magnetic, mechanical and quench protection study of the four type of dipole coil configurations; conceptual design study of the high field quadrupoles.  Development of a 12-T Nb 3 Sn model magnet Magnetic and mechanical design; High J c Nb 3 Sn R&D and production; Rutherford cabling; Coil fabrication (winding, heat reaction, impregnation, joints); Mechanical support structure and assembly; Test facility for high field accelerator magnets (field measurement, quench protection, power supply, cryostat, …).  Development of YBCO model coils YBCO conductor R&D and production; Fabrication of high field YBCO coils (field quality optimization, cabling, joint,…); Quench protection study.  Development of a Bi-2212 model coils Bi-2212 conductor R&D and production; Fabrication of high field Bi-2212 coils; Quench protection study.