care-hhh-amt workshop on heat generation & transfer in superconducting magnets paris, november...

CARE-HHH-AMT Workshop on Heat Generation & Transfer in Superconducting MagnetsCARE-HHH-AMT Workshop on Heat Generation & Transfer in Superconducting Magnets Paris, November 190th 2007Paris, November 190th 2007 11

Experience at CEAExperience at CEA

Jaroslaw Polinski, Bertrand Baudouy

CEA/Saclay

CARE-HHH-AMT Workshop on Heat Generation & Transfer in Superconducting MagnetsCARE-HHH-AMT Workshop on Heat Generation & Transfer in Superconducting Magnets


• NED cryostat

• Stack experiment– Saclay sample with conventional insulation (Kapton)

– KEK sample with ceramic insulation

• Drum experiment – fiberglass-epoxy material as new conventional insulation

Contest


Stack experiment

• Saclay sample construction


Stack experiment


Dummy conductors

• Material: Stainless Steel

• Dimensions: 2.5mm x 17mm x 150mm (Tx W x L)

• Central surface part machined to real cable geometry

• Allan Bradley temp. sensors placed in the quarter and half of the conductor length


Stack experiment


Conventional Kapton insulation

• 1st layer: Kapton 200 HN (50 μm x 11 mm) in 2 wrappings (no overlap) • 2nd layer: Kapton 270 LCI (71 μ m x 11 mm) with a 2 mm gap• Thermally treatment at 170oC for polymerisation


Stack experiment

• Conventional Kapton insulation

Tests conditions

• 17 Tons on the samples as specified• Temperature of the bath Tb= 1.8K, 1.9K and 2.0K• Only central conductor heated• Supplied current range: 0 – 10 Amps• Dissipated heat range: 0 – ≈30 mW/cm3


• Conventional Kapton insulation test results– Temperature of the heated conductor

Stack experiment

0

200

400

600

800

1000

1200

1400

0 5 10 15 20 25 30 35

Power, mW/cm3

T-T

b,

mK 1.8K

1.9K

2.0K


• Conventional Kapton insulation test results– Temperature of the neighbour conductors

Stack experiment

0

10

20

30

40

50

60

70

80

90

0 5 10 15 20 25 30 35Power, mW/cm3

T-T

b,

mK

Layer IV

Layer II

TIII=T

TIII<T

TIII>T


• Technical solution investigation

Stack experiment



Stack experiment

20 kN ≈10 MPa

Vacuum grease – thermal blockade G10 interlayer spacer

0.9 mm

Spacer



Tb=1.9K

0

200

400

600

800

1000

1200

1400

1600

1800

0 5 10 15 20 25 30 35Power, mW/cm3

T-T

b,

mK

1.9K-unins

1.9K-one side insul

1.9K G10

T

Stack experiment


Stack experiment

• KEK sample construction


Stack experiment


Dummy conductors

• Material: CuNi

• Dimensions: 1.9mm x 11mm x 150mm (Tx W x L)

• Conductor fabricated in real cable technology

• CERNOX temp. sensors placed in the quarter of the conductor length


Stack experiment


Ceramic (innovative) insulation

• One layer of

• Treated for 50 hours at 666oC at 10 MPa


0

5

10

15

20

25

30

35

0 5 10 15 20 25 30 35 40 45

Power, mW/cm3

T-T

b,

mK

1.8K

1.9K

2.0K

Stack experiment


Ceramic (innovative) insulation10 MPa on the samples as specified


Heat Transfer Experiments

DRUM SETUP



• Drum setup– Theoretical Background of the Method (1/2)

TR

TTR

TTh

TTl

TTh

AQ

sbi

snb

nk

nniK

S 11

2

21

1

A – Active area of the heat transferhk – Kapitza heat transfer coefficientλ – Thermal conductivity of the materiall – material thicknessRs – overall thermal resistance of the sampleTi – temperature of the inner volumeT1 – temperature of the sample surfaces from the

inner volumeT2 – temperature of the sample surfaces from the

cryostat bathTb – temperature of the cryostat bath

Ti

T2

T1

Tb

Qs

A

l

Inn

er

vo

lum

e

Cry

os

tat

ba

th



• Drum setup– Theoretical Background of the Method (2/2)

111 TTThnTTh i

niK

nniK

bnbK

nb

nK TTThnTTh

21

2

l

Rl

ThnThnl

ThnQTA

RK

nbK

nbK

niKs

s

2211111

Since T>>Tb it can be assumed that:

And finally overall thermal resistance of the sample:



• Drum setup– Construction of the 1D support for thermal resistance in

HeII Tests

T i

T bCompressing flange

Sample holder flange

Support flange

Support blind flange Feeding tube(Capillary)

Insulation materialsample

HeaterAB T emperature

Sensor

Scotch-Weld DP190Epoxy seal

80

Pressurised superfluidhelium bath

Inner helium volume

Sample holder flange Support flange



• RAL insulation - fiberglass tape and epoxy resin

Tested sheets Sheet surface photo



• RAL insulation– Study of sheets surface area and thickness

lh

H

Thickness determination

Wy

WxHyxf

2sin

2sin2/,

Surface mathematical description

H

W

Surface roughness tester result

Surface Roughness Tester


0.00

0.01

0.02

0.03

0.04

0 0.02 0.04 0.06 0.08 0.1 0.12Heat flux through sample Q s, W

T

=Ti-

Tb

, K Tb=1.55 K

Tb=1.6 K

Tb=1.7 K

Tb=1.8 K

Tb=1.9 K

Tb=2.0 K

Tb=2.05 K


• RAL insulation– Computation process, Example for l=0.055 mm

Evolution of the temperature difference across the sample with heat flux as a function of the bath temperature.

where

bQaT S

A

Ra s

y = 0.5673x - 0.0013


y = 37.62x + 0.00522

0.000

0.002

0.004

0.006

0.008

0.010

0.012

0.014

0.016

0.018

0.020

0.00000 0.00005 0.00010 0.00015 0.00020 0.00025 0.00030 0.00035 0.00040Material thickness l , m

To

tal

term

. re

sist

ance

Rs,

m²K

/W

1.55K

1.6K

1.7K

1.8K

1.9K

2.0K

2.05K


• RAL insulation– Computation process

Ks R

lR21



• RAL insulation– Thermal conductivity, comparison with other materials

y = 0.0251x - 0.0118

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

0.045

0.050

1.5 1.6 1.7 1.8 1.9 2 2.1

Temperature, K

Th

erm

al c

on

du

ctiv

ity

W/m

K

Ral insulation

Kapton

Epoxy

Quartz glass

G-10 (Fiber glass + Epoxy)



• RAL insulation– Kapitza Resistance

y = 0.00514x-1.58

y = 0.00854x-2.57

0

0.0005

0.001

0.0015

0.002

0.0025

0.003

1.5 1.6 1.7 1.8 1.9 2 2.1

Temperature, K

Kap

itza

res

ista

nce

m²K

4 /W

RAL insulation

Kapton

n

KK T

hnR

11


• September 2006 - October 2007

– Test of Saclay sample (17 tons compressed)

– Test of Saclay sample with one flank side thermally insulated with APIEZON greases

– Test of first ceramic insulation stack sample (10 MPa load)

– 1D: Tests of RAL insulation In HeII

– Test of Saclay sample with one flank side thermally insulated with G10 interlayer spacer

• From November 2007

– Ceramic insulation with different loads

– Thickness of the RAL insulation materials

Tests Summary

care-hhh-amt workshop on heat generation & transfer in superconducting magnets paris, november...

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