Zian Zhu Magnet parameters Coil/Cryostat/Support design Magnetic field analysis Cryogenics Iron yoke structure Mechanical Integration Superconducting Magnet

Zian Zhu

• Magnet parameters

• Coil/Cryostat/Support design

• Magnetic field analysis

• Cryogenics

• Iron yoke structure

• Mechanical Integration

Superconducting Magnet & Mechanical Integration

BESIII Technical Review, Sep 16~17, 2002, Zian Zhu

Basic Parameters(1)• Physics requirement• Central field B = 1.0 T

• Dimension of magnet(RT volume): L = 3.89 m, D = 2.65 m

• Uniformity B/B < 5% in the tracking volume

• Cool-down time t < 10 days

• Configuration• Single layer solenoid coil, steady field

• In-direct cooling by two phase flow liquid helium

• Pure aluminum based stabilizer

• NbTi/Cu superconductor

• Ramp rate: reached to operating current in 0.5hours

• Recovery time: <1 day

• Field stability: 5×10-4



Basic Parameters(2)Cryostat

Inner radius 1.325m

Outer radius 1.7m

Length 3.89mCoil

Effective radius 1.45m

Length 3.5m

Cable dimension 3.7mm*20mm

Electrical parameters

Central field 1.0T

Nominal current 3150A Inductance 2.0H

Stored energy 9.2MJ

Cold mass 3.5ton

Total Weight 14.6tonRadiation thickness 1.86X0



Coil Design(1)

4N Purity aluminum-stabi1izerRRR=~300

nIB 00

Cross section of the superconducting cable

mm05.007.3

921 turns for a 3.5m long coil

lDB

lSB

VBHE 42

1

2

1)

2

1(

2

0

2

0

2

= 9.2MJ

mm1.0020

nD

BnSB 4

2dt

dIL

dt

d

I

L

= 2H

EVh EtlDh

Dlh

Et

20mm

32.470 /2.16/6000 mMJkgJhhh KK

,w=3.7mm

,I=3150A

Working 3150A@1T-----Critical 6300A@2TNbTi wire， JC=3800A/mm2@2T, NbTi/Cu ratio

1.09:1Cross Section Area of NbTi/Cu: 3.2mm2

3.2mm2



Coil Design(2)Stress in the Coil

0

2

2Z

r

BP

t

rB

t

rP Zrh

0

2

2 Hoop stress

Radial Magnetic Pressure

t is thickness of coil plus support cylinder

When thickness of support cylinder is 20mm, t=35mm

Maximum hoop stress is 19 Mpa



Coil Design(3)Other analysis

Esti mati on of the vol tage by quench

0. 050. 0

100. 0150. 0200. 0250. 0300. 0350. 0

1 2 4 8 10 20 30Quench Length (m)

Coil

Vol

tage

(mV

)

Voltage versus length of quench area in the coil

Coil Ohmic heat by the joints: 2.54 mW



Coil Design(4)

Coil Cross Section



Magnetic field analysis(1)

Flux line

End Yoke L1~L9 30,30,30,30,30,40,80, 80,80mm

Barrel Yoke L1~L9 30,30,30,40,40,80,80,80,150mm

gaussmB

MDCB

B

545.3@

%2@

When anti-solenoid excited

%13@

MDCB

B



Magnetic field analysis(2)

Field Uniformity in the Drift Chamber



Magnetic field analysis(3)Fringe field analysis



By following methods:

1. Adopting “Cap” construction on the gap

2. Increase the thickness of barrel yoke layer9 from 8 cm to 15 cm

3. A magnetic shield near ISPB region

4. Connect the shield to pole tip magnetically can decrease the fringe field further.

B along beam axis

Cryostat Design(1)

Material: SUS316L

)()()1(

855.0

2

5

4

32

r

l

t

r

Epcr

Buckling check

Outer cylinder,Inner cylinder,End plates

1cr

c

crP

P

Buckl i ng Check of the Outer Vessel

02468

101214

10 11 12 15 16 18

Thi ckness (mm)

Pcr

kg/m

m2

ANSYSNASA

Mechanical strength check



Cryostat Design(2)

Max. Stress: 43 MPa

Max. Deformation: 0.18mm

Thickness: Outer vessel =16 mm Inner vessel = 5 mm End vessel = 32 mm



Coil Support Structure(1)

12 radial support rods6 at each end

12 axial support rodsat chimney side

Rods material: GFRP



Coil Support Structure(2)Axial decentering force 416340 N/5cm

Radial decentering force 34695 N/5cm

Diameter of the rods for the nitrogen shield is 15mm,6mm for radial and axial support.



Weight and Radiation thickness



Cryogenics(1)



Cryogenics(2)

Cooling Type Normal: Forced 2-Phase Helium Cooling Trouble: Thermo-syphon Cooling

Volume of Working Fluid Coil: 50 LService Port: 200 LShield: 16 L

Coil Pipe Outer Diameter: 31 mmInner Diameter: 25 mmTotal Length: 102 mNumber of Line: One

Shield Pipe Outer Diameter: 18 mmInner Diameter: 14 mmTotal Length: 70 mNumber of Line: Two (One for each side)



Cryogenics(3)



Iron Yoke(1)



Design outline:

Occupy smallest Muon space,

Less assembly time,

Limit by 3.7m height from IP to ground,

Field uniformity in the tracking volume ,

Fringe field requirement

Iron Yoke(2)



End Yoke L1~L9

30,30,30,30,30,40,80, 80,80mm

Barrel Yoke L1~L9

30,30,30,40,40,80,80,80,150mm

Cryostat support structure



Mechanical Integration(1)Main Requirements of the design:

(1) Provide support and adjustments for all sub-detectors

(2) Provide easy installation and reasonable gaps between neighboring sub-detectors both in radial and longitudinal directions.

(3) Convenient access to sub-detectors for maintenance without breaking the accelerator vacuum.

Door opening, Endcap EMC/TOF moving

(4) The re-position of the end iron yoke should guarantee no change of the magnet field.

(5) Provide route and space for cables, cooling pipes and gas pipes

(6) Minimize the fringe field along beam direction



Concept Design of BESIII Superconducting Magnet

Mechanical Integration(2)


cos=0. 93cos=0. 83

S10

F1

1005100

5700

2550

2050

2800

3480

1100

( 45mm)每端缩短1235

40. 2

40

R930

R925

R810

11

1291

R400

R350

R400

R871

R838

R482

.5

1720

1721

24. 5

1750

2050

13801330







Barrel yoke: Max. Stress: 15.5 MPa Max. Deformation: 0.24 mm




Barrel Yoke Assembly Lifting: Max. Stress: 73 MPa Max. Deformation: 0.4 mm




Base: (in the middle of main beam) Max. Stress: 93.5 MPa Max. Deformation: 6 mm




Sub-detector support cylinder: Max. Stress: 98 MPa Max. Deformation: 0.5 mm

Acknowledgement

Design group members:

Prof. S.Xu, Prof. X.Liu, Prof. J.Bai, L.Wang, S.Han, C.Wei, Q.Ji, W.Song, H.Guo, L.Liu, Z.Hou

KEK experts group:

Prof. H.Tsuchiya, Y.Makida, H.Yamaoka.



Thanks!

Documents

Zian Zhu Magnet parameters Coil/Cryostat/Support design Magnetic field analysis Cryogenics Iron yoke structure Mechanical Integration Superconducting Magnet