R&D Progress

of the High Field Magnet Technology

for CEPC-SPPC

Qingjin XUOn behalf of the SppC magnet working group

Institute of High Energy Physics (IHEP)Chinese Academy of Sciences (CAS)

2015.9.11

a) Magnetic design study of the 20-T dipole

b) Mechanical design study of the 20-T dipole

c) Fabrication of high Jc Nb3Sn 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

Number of apertures (-) 2Aperture diameter (mm) 50Inter-aperture spacing (mm) 330Operating current (A) 14700Operating temperature (K) 1.9Operating field (T) 20Peak field (T) 20.4Margin along the loadline (%) ~20Stored magnetic energy (MJ/m) 7.8Inductance (magnet) (mH/m) 72.1Yoke ID (mm) 260Yoke OD (mm) 800Weight per unit length (kg/m) 3200Energy density (coil volume) (MJ/m3) 738Winding pack current density (A/mm2) 400Force per aperture – X/Y (MN/m) 23.4/2.4Peak stress in coil (MPa) 240Fringe Field @ r = 750 mm (T) 0.02

Magnetic design study of a 20-T dipole20-T Nb3Sn + HTS common coil dipole for SppC Space for beam pipes: 2 * Φ50 mm; load line ratio:

~80% @ 1.9 K; yoke diameter: 800 mm

Nb3Sn Nb3SnHTS

Nb3Sn Nb3SnHTS

Iron

With 10-4 field quality @ 2/3 aperture

Main Design Parameters

Magnetic design study of a 20-T dipoleIntegrated multiples with optimized coil ends

0 200 400 600 800 1,000 1,200

-350

-250

-150

-50

50

150

250

350b3 b5 b7a2 a4 a6

(mm)

20-T coil end design with common coil configuration Integrated bn/an Value (10-4)

b3 0.14

b5 1.42

b7 -0.40

a2 -0.29

a4 -1.81

a6 0.03

Beam pipes: 2 * Φ50 mm Load line ratio: ~80% @ 1.9 K Yoke diameter: 800 mm

Chengtao Wang

Different coil configurations for 20-T dipole

Left: Common coil Right: Cos-theta

Common coil

Cos-theta

Coil endsCommon coil Cos-theta

Magnetic design study of a 20-T dipole

Yoke

V-pad

V-key

Iron

Bi2212 + Nb3Sn 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

dipoleKai Zhang

Mechanical design study of a 20-T

dipoleKai Zhang et al. AL 7075

Yoke

H-pad

V-pad

Dummy coil

(Aluminum bronze)

Cross section of a Nb3Sn 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

Fabrication of high Jc Nb3Sn wires (WST)

High Jc Nb3Sn development at WST

~ Non-Cu Jc > 2500 A/mm2

@ 12 T, 4.2 K !

cross-section of the wire

Internal-Tin process

Available by Oct. 2015!

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

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。

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

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

Running current 93A

13

Quench AreaBz

Operating Current 70A

Coupling-loss Protection

thermaldisturbance

electricaldisturbance

completely quench point

Yinan Hu et al.

Quench protection for high field magnets

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

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 Nb3Sn model magnetMagnetic and mechanical design; High Jc Nb3Sn 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 coilsYBCO 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 coilsBi-2212 conductor R&D and production; Fabrication of high field Bi-2212 coils; Quench protection study.