Preliminary Design for the Coupling Coil Cryostat in MICE

MICE CM16 2006.10, CCLRC/UK

Li Wang

Preliminary Design for the Coupling Coil Cryostat

in MICE

Institute of Cryogenics and Superconductivity Technology

Harbin Institute of Technology

P.R.China


Li Wang

According to the “Technical Specification on MICE Coupling Solenoid

Magnet Fabrication, Assembly, Test and Shipping”, ICST/HIT carried out t

he preliminary engineering design on the coupling magnet cryomodule si

nce this August. The following persons have been involved in the current

design in ICST.

Dr. Lin X.Jia, Professor

Dr. Li Wang, Professor

Mr. C.S.Liu, Engineer

Mr. G. Hang, Engineer

H.Wu, Ph.D. candidate, numerical calculation

L.K.Li, M.S. candidate, numerical calculation

The detailed calculations and numerical simulations are going on.


Li Wang

The presented include:

Process flow diagram

Cryostat

Helium vessel

Self-centered supports

Current leads


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Flow Diagram

LHe dewar

GHe storage tank

Coupling magnet cryomodule

Vacuum pumping

Cryo-cooler

He compressor


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The precooling or test system is composed of

• LHe dewar (250L, 500L available in ICST )

• LN2 dewar (if necessary, 200L, 500L available in ICST )

• GHe storage tank (5m3, 10m3 available in ICST )

• He compressor

• Transfer lines

• Safety device (relief valves, rupture disc etc.)

• Valves

• Vacuum pumping system (available in ICST )

• Cooling water system (available in ICST )


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Schematic of coupling magnet precooling system


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Cryostat

The cryostat is composed of

• Vacuum chamber made of stainless steel

• Radiation shield made of annealed OFHC copper

• Helium vessel made of stainless steel or 6061-T6 Aluminum

• Coil assembly consisting of NbTi/Cu SC conductors, bobbin, ground insulation, epoxy and support cylinder (or banding)

• Copper leads + HTS leads

• Supports

• LHe condenser

• Cryo-cooler

• Piping

• Bayonets and fittings

• Feedthroughs for temperature sensors, heater, level meter, voltage taps etc.

• Instrumentation including temperature sensors, heater, level meter, pressure transducers etc.

• MLI insulations and electrical insulations


Li Wang

Cryo-cooler

Helium vessel

Vacuum vessel

LHe piping

Cold-down supply piping

Shields

Supports

VHe pipingCold-down return piping

Vacuum port

Feedthrough


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Copper lead

1st stage cold head

HTS lead

2nd stage cold head

Eddy current interrupt slot

Supports

Flexible Cu strap

Bayonet

Piping to relief device

Condenser


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Up to the magnetic field distribution, the location of HTS leads and cryocooler will be changed.


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Radiation shield is divided into four parts for assembly.


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He vessel Bobbin

Coil

Support cylinder


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Magnet cryostat components


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Helium Vessel

Option A

Directly made of coil bobbin, end plates and cover cylinder

Coil is cooled through conduction

Simple structure, but thick Al material needed

A separated vessel to contain the coil assembly

Coil is cooled either through conduction or directly by LHe

Complex structure and assembly

Option B


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Two cooling schemes for Option B:

Temperature distribution

SS vessel wall

Liquid helium

SS Support cylinder

Coil

Ground insulation

Al Bobbin

4.2K

q-radiation=0.2W/m2

Helium vessel is made of stainless steel.

The coil is cooled through conduction by liquid helium.

SS thickness=15mm

△Tcoil<0.1K


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The coil is cooled directly by liquid helium.

4.2K

q-radiation=0.2W/m2 Tcoil<0.066K△


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Helium passage

Helium passage

Bobbin

Coil

Support cylinder


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SS vessel wall

Liquid helium

Al Support cylinder

Coil

Ground insulation

Al Bobbin

4.2K


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4.2K

The coil is cooled directly by liquid helium.



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15mm SS in thickness

Supports

Stress analysis for Option B: to consider the radial, longitudinal and gravity forces as well as the 4 bara pressure inside.


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Li Wang

To only consider the 4 bara pressure inside for SS helium vessel.


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Option A: directly made of coil bobbin, end plates and cover cylinder

6061-T6 Al

6061-T6 Al

4.2K


q-radiation=0.2W/m2 Tcoil=0.04K△ Al thickness=25mm


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25mm Al in thickness

Supports

Stress analysis for Option A: to consider the radial, longitudinal and gravity forces as well as the 4 bara pressure inside.


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To only consider the 4 bara pressure inside for Al helium vessel.


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Self-centered Supports


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Supports without 50K intercept

16mmx12.5mm, 175mmx2

G-10 band SS

~50K


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Supports with 50K intercept

~50K


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Total

50K Cold Mass Support Heat Load (W) 0.13162 1.05296

4.2K Cold Mass Support Heat Load (W) 0.008686 0.069488

Total

Total Heat Leak from the Cold Mass Support (W)

0.074348 0.594784

Heat loads from cold mass supports

Supports with 50K intercept

Supports without 50K intercept

The structure and dimensions of the supports need to be further optimized.


Li Wang

Current leads

The current lead for coupling coil consists of a conduction-cooled copper lead that carries current from room temperature to intercept temperature (the first stage of cryocooler) and a HTS lead that carries current from the intercept to the coil.

Copper lead

HTS lead


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Design for Copper current leads

dz

TL

z

Q+dQ

Q

I

TH

2( )*0

dQ T I

dz A

* ( )*dT

Q A k Tdz

2 2 22 ( ) ( )H

L

T

L H TQ Q I k T T dT

;

;

,

,L L

H H

T T Q Q

T T Q Q

2 ( ) ( )H

L

Topt

T

Qk T T dT

I

Energy equation:

(1)

(2)

(3)

0HQ Assuming:

(4a)

( )

( )

H

L

T

T

L k TdT

A Q T (5)

( )

2 ( ) ( )

H

HL

T

TTopt

T

LI k T dT

A k T T dT

(6a)

0 ( )H

L

T

I T

AQ k T dT

L

The optimized heat flow into the cold end of the lead:


Li Wang

2 20 ( )opt

H L

QL T T

I

2 20

1 ( )H

L

T

Topt H

LI k T dT

A L T T

0( ) ( )k T T L T To apply Wiedemann-Franz law for most metal and alloy,

(4b)

(6b)

40 45 50 55 60 65 7011.2

11.3

11.4

11.5

11.6

11.7

11.8Qopt(W) ~TL(K) at I=250A

Cold temperature [K]

Opt

imiz

ed h

eat f

low

[W]

11.8

11.2

Q opt T L

7040 T L

200 210 220 230 240 250 260 270 280 290 30010

11

12

13

14

15

16

17

18

19

20L/A(mm-1)~I(A)at 50K, 60K

Current [A]

L/A

[m

m-1

]

20

10

F opt50K I( )

F opt60K I( )

300200 I


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200 210 220 230 240 250 260 270 280 290 3008

9.5

11

12.5

14Qopt(W) ~I(A) at 50K, 60K

Current [A]

Opt

imize

d he

at flo

w[W

]

14

8

Q opt50K I( )

Q opt60K I( )

300200 I

For I=250A

TL=50K, Qopt=11.563W

TL=60K, Qopt=11.49W

For I=220A




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Material RRR Nominalcurrent

Maximumcurrent

Size

D L

pure copper 10 220A 250A 8mm 0.4m

Parameters used for numerical simulation of the copper lead by FLUENT

I=250A, D=8mm, L=0.4m, Q=14.27W


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Temperature distribution along the copper lead at I=300A, D=8mm, L=0.4m

Q=15.245W


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T-warm-end>300K


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TypeOuter

Diameter (mm)Length (mm)

Cross-sectionarea ( mm2)

CriticalCurrent (A/77K)

Silver contactlength (mm)

CSL-18/80.3 18.0 80 78 750 15

CSL-18/120.3 18.0 120 78 750 15

CSL-18/160.3 18.0 160 78 750 15

Parameters of HTS Current Leads

*Data from Sumitomo Electric

Superconducting tubes of BiPbSrCaCuO (Bi-22

23 phase) ceramics with silver covered ends of

a low contact resistance are suitable for current

leads effectively reducing heat leak into superc

onducting magnets. For better mechanical prot

ection the leads may be encased in metal or G-

10 tubing.

The nominal current for the HTS lead is 220A, and it must be capable of carrying 500A when the high-temperature end of the lead is nominally at 60K and at 1.5T.


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60 80 100 120 140 160 180 2000

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08Heat load along the HTS lead

Length of HTS [mm]

Hea

t loa

d [W

]0.08

0

Q HTS x( )

20060 x

H

L

T

TdTTk

L

AQ )(


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Heat loads from the current leads

HTS leads (50K-4.2K)

L (mm) Do (mm) Thickness (mm) Q (W)

80 18.0 1.505 0.0573*2

120 18.0 1.505 0.0382*2

160 18.0 1.505 0.0286*2

Copper leads (300K-50K)

I (A) L (mm) D (mm) Qopt (W)Qopt (W)

w/o current

(L/A)opt

(1/mm-1)Qreal (W)

Qreal (W)

w/o current

(L/A)real

(1/mm-1)

300 400 8.00 13.876*2 8.587*2 11.781 15.245*2 12.712*2 7.958

27.752 17.174 30.49 25.424

250 400 8.00 11.563*2 7.156*2 14.137 14.27*2 10.527*2 9.610

23.126 14.312 28.54 21.054

Since the performance of HTS leads will be greatly influenced by the magnetic field, we should consider it while to select the commercial leads.


Li Wang

Winding Process

Winding procedure and materials to be used need further detailed discussion.


Li Wang

The detailed further calculations and analyses are g

oing on provided no change on the coil design such as t

he coil itself and its quench protection, vacuum vessel,

supports, helium condenser, piping, safety device, instr

uments, interface to RF cavity module and so on.


Li Wang

ICST contribution summary up to date

Two professors (one half time and one quarter time)

Two engineers (one and a half time)

Two graduates (full time)

ICST future possible contributions (year’07)

Research fund $10k

Three professors (two half time and one quarter time)

Four engineers (full time)

Three graduates (full time)

Four mechanical/cryogenic technicians (full time)


Li Wang

THANK YOU

Preliminary Design for the Coupling Coil Cryostat in MICE

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