NED heat transfer program at CEA
Jaroslaw Polinski, Bertrand Baudouy
CEA/DAPNIA/SACM
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
1
Contest
• Motivations of the program
• Cryostat NED
• Conventional insulation (Kapton) – Saclay sample
• Ceramic (innovative) insulation – KEK sample
• RAL conventional insulation – drum method
• Technical solutions investigation
• Conclusions
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
2
Contest
• Motivations of the program
• Cryostat NED
• Conventional insulation (Kapton) – Saclay sample
• Ceramic (innovative) insulation – KEK sample
• RAL conventional insulation – drum method
• Technical solutions investigation
• Conclusions
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
3
Motivations of the program
• Operation of the SC accelerators is connected with energy
deposition in SC cables due beam losses
– Current (NbTi) LHC – e ≈ 0.4 – 0.6 W/m, 10 – 15mW/cm3
– Future (Nb3Sn) LHC – e ≈ 2 – 3 W/m, 50 – 80mW/cm3
– Max temperature of the SC cable ≈ 3.3K
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
4
Motivations of the program
LHC NbTi
Exemplary experimental results for different configuration of the polyimide (Kapton) insulation
B. Baudouy et al., Heat transfer in electrical insulation of LHC cables cooled with superfluid helium, Cryogenics 39, Elsevier 1999
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
5
Motivations of the program
• Operation of the SC accelerators is connected with energy
deposition in SC cables due beam losses
– Current (NbTi) LHC – e ≈ 0.4 – 0.6 W/m, 10 – 15mW/cm3
– Future (Nb3Sn) LHC – e ≈ 2 – 3 W/m, 50 – 80mW/cm3
– Max temperature of the SC cable ≈ 3.3K
• Nb3Sn technology need the thermal treatment over 600oC
– Polyimide (Kapton) insulation operation temperature > 400oC
NEW GENERATION MAGNETS CALL FOR NEW MATERIALS FOR
SC CABLES ELECTRICAL INSULATIONS
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
6
Contest
• Motivations of the program
• Cryostat NED
• Conventional insulation (Kapton) – Saclay sample
• Ceramic (innovative) insulation – KEK sample
• RAL conventional insulation – drum method
• Technical solutions investigation
• Conclusions
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
7
Cryostat NED
Vacuum
pump
1 bar, T=4.2K
He I
Cryostat scheme
Tl
T » T?
(cooperation with WUT)
Recuperative
heat exchanger
Constriction
Lambda
valave steam
He II
T=1.7-2.2 K
Foam insulation
Cryogenic
vessel
Lambda plate
supports
Vacuum
container
Expansion
valve
Cooling
Heat exchanger
pipe
Claudet bath principle
Radiation
shields
Heat
exchanger
External
radiation shield
He I
He IIp
He IIs
SUPERCRITICAL
He
He I
103
Lambda plate
Internal radiation
shield
SOLID
Expansion
valve
Pressure [kPa]
Lambda
valve
104
He II
Cr
T=1.9 K
p=100 kPa
102
Sasturated He I
PRESSURIZED
He II
10
T=4.2 K, p=100 kPa
l POINT
VAPOR
T=2.2 K, p=5 kPa
He IIp vessel
Sasturated He II
T=1.8 K, p=1.6 kPa
1
1
He IIs vessel
2
3
4
5
6
Temperature [K]
Helium phase diagram
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
8
Cryostat NED
Experimental setup at CEA Saclay
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
9
Cryostat NED
Difference between setpoint and measurement (mK)
Performance of the NED cryostat
4
10 mn
6,1 W
2
7,6 W
4,9 W
0
10 mn
5 mn
7,6 W
-2
20 mn
8,3 W
30 mn
-4
1,6
1,7
1,8
1,9
2,0
Température (K)
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
10
Contest
• Motivations of the program
• Cryostat NED
• Conventional insulation (Kapton) – Saclay sample
• Ceramic (innovative) insulation – KEK sample
• RAL conventional insulation – drum method
• Technical solutions investigation
• Conclusions
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
11
Conventional Kapton insulation
Insulation description
•
•
•
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
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
12
Conventional Kapton insulation
Dummy conductors
•
•
•
•
Material: Stainless Steel
Dimensions: 2.5mm x 17mm x 150mm (T x 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
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
13
Conventional Kapton insulation
Tests conditions
•
•
•
•
•
•
5 conductors stack, 17 Tons on the samples as specified
Temperature of the bath Tb= 1.8K, 1.9K and 2.0K
Only conductor III (central) heated
Supplied current range: 0 – 10 Amps
Dissipated heat range: 0 – ≈30 mW/cm3
T measured at the centre of conductors II, III and IV
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
14
Conventional Kapton insulation
Saclay sample
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
15
Conventional Kapton insulation
Test results – comparison with CERN results
– Temperature of the heated conductor (conductor III)
1400
I
II
III
IV
V
1200
TIII
1000
T-Tb, mK
Tb=1.8K
800
Tb=1.9K
Tb=2.0K
600
CERN Results Tb=1.9K
400
200
0
0
5
10
15
20
Power, mW/cm3
25
30
35
For Q=10 mW/cm3 (NbTi) – DT≈50 mK
For Q=50 mW/cm3 (Nb3Sn) – DT≈2.2K !!!
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
16
Conventional Kapton insulation
Test results
– Temperature of the conductors II and IV, adjoining to heated
conductor
Tb=2.0K
90
80
I
II
III
IV
V
70
T-Tb, mK
60
TII
TIV
50
TIII<Tl
40
TIII=Tl
30
Layer IV
Layer II
20
10
0
0
5
10
15
20
Power, mW/cm 3
25
30
35
TIII>Tl
Typically temperature characteristic for conductors adjoining to heated conductor
Exemplary modeling results
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
17
Contest
• Motivations of the program
• Cryostat NED
• Conventional insulation (Kapton) – Saclay sample
• Ceramic (innovative) insulation – KEK sample
• RAL conventional insulation – drum method
• Technical solutions investigation
• Conclusions
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
18
Ceramic (innovative) insulation
Insulation material
•
•
Mineral fibre tape vacuum impregnated with epoxy resin
Treated for 50 hours at 666oC at 10 MPa
Single cable and sack of cables with ceramic insulation – photo F. Rondeaux
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
19
Ceramic (innovative) insulation
Dummy conductors
•
•
•
•
Material: CuNi
Dimensions: 1.9mm x 11mm x 150mm (T x W x L)
Conductor fabricated in real cable technology
CERNOX temp. sensors placed in the quarter of the length and in axis
of the conductor
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
20
Ceramic (innovative) insulation
Test condition
•
•
•
•
•
•
10 MPa on the samples as specified
Temperature of the bath Tb= 1.8K, 1.9K and 2.0K
All conductors heated
Supplied current range: 0 – 10 Amps
Dissipated heat range: 0 – ≈42 mW/cm3
Temperature measured on the central conductor
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
21
Ceramic (innovative) insulation
KEK sample
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
22
Ceramic (innovative) insulation
Test results
35
30
T-Tb, mK
25
20
15
1.8K
1.9K
10
2.0K
5
0
0
5
10
15
20
25
30
35
40
45
Power, mW/cm 3
For Q=10 mW/cm3 (NbTi) – DTmax<10 mK
For Q=50 mW/cm3 (Nb3Sn) – DT<35 mK !!!
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
23
Contest
• Motivations of the program
• Cryostat NED
• Conventional insulation (Kapton) – Saclay sample
• Ceramic (innovative) insulation – KEK sample
• RAL conventional insulation – drum method
• Technical solutions investigation
• Conclusions
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
24
RAL insulation
Construction of the drum test support
 80
Tb
Compressing flange
Pressurised superfluid
helium bath
Sample holder flange
Insulation material
sample
Scotch-Weld DP190
Epoxy seal
Support flange
Ti
Support blind flange
Inner helium volume
Heater
AB Temperature
Sensor
Sample holder flange
Feeding tube
(Capillary)
Support flange
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
25
RAL insulation
Drum setup
– Theoretical Background of the Method (1/2)
Ti

A
Qs
T2
Tb
l
Constant T bath
Heated volume
T1
hK Ti n  T1n

QS  l
  T1  T2 
A l
hk T2n  Tbn




1
Ti  Tb   1 TD
Rs
Rs
A – Active area of the heat transfer
hk – Kapitza heat transfer coefficient
λ – Thermal conductivity of the material
l – material thickness
Rs – overall thermal resistance of the sample
Ti – temperature of the heated volume
T1 – temperature of the sample surfaces from the
heated volume side
T2 – temperature of the sample surfaces from the
constant T bath
Tb – temperature of the constant T bath
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
26
RAL insulation
Drum setup
– Theoretical Background of the Method (2/2)
Since DT>>Tb it can be assumed that:

T

» nh
hK Ti n  T1n » n  hK  Ti n 1 Ti  T1 
hK
n
2
 Tbn
K
 Tbn 1 T2  Tb 
And finally overall thermal resistance of the sample:
Rs 
ADT
1
l
1
2
l
2
l



»

»

Qs
n  hK  Ti n 1 l n  hK  Tbn 1 n  hK  Tbn 1 l RK l
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
27
RAL insulation
• RAL insulation material - fiberglass tape and epoxy
resin
Sheet surface photo
Tested sheets
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
28
RAL insulation
Study of sheets surface area and thickness
 2 
 2 
f x, y   H / 2  sin  x
  sin  y

 W 
 W 
Surface Roughness Tester
Surface mathematical description
H
H
h
l
W
Thickness determination
Surface roughness tester result
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
29
RAL insulation
Tests conditions
•
•
•
•
•
4 sheets with different thicknesses
7 different temperatures of the bath from range: 1.55 K – 2.05 K
Temperature of the inner volume: Tb – Tl
Heat dissipated in inner volume: 0 – 0.8 W
Range of DT accounted in computation process: 10 – 30 mK
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
30
RAL insulation
Test results and computation process, example for
l=0.055 mm
0.04
DT=Ti-Tb, K
0.03
y = 0.5673x - 0.0013
0.02
DT  a  QS  b
0.01
where
a
Rs
A
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
0.00
0
0.02
0.04
0.06
0.08
Heat flux through sample Q s , W
0.1
0.12
Evolution of the temperature difference across the sample with heat flux as a function of the bath temperature.
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
31
RAL insulation
Computation process
0.020
Total term. resistance Rs , m²K/W
0.018
0.016
0.014
Rs 
1
l
l 
2
RK
y = 37.62x + 0.00522
0.012
1.55K
0.010
1.6K
0.008
1.7K
0.006
1.8K
0.004
1.9K
2.0K
0.002
0.000
0.00000
2.05K
0.00005
0.00010
0.00015 0.00020 0.00025
Material thickness l , m
0.00030
0.00035
0.00040
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
32
RAL insulation
Thermal conductivity, comparison with other materials
0.050
Thermal conductivity W/mK
0.045
0.040
0.035
y = 0.0251x - 0.0118
0.030
Ral insulation
0.025
Kapton
0.020
Epoxy
Quartz glass
0.015
G-10 (Fiber glass + Epoxy)
0.010
0.005
0.000
1.5
1.6
1.7
1.8
Temperature, K
1.9
2
2.1
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
33
RAL insulation
Kapitza Resistance
Kapitza resistance m²K 4/W
0.003
0.0025
y = 0.00514x -1.58
0.002
RK 
0.0015
1
T 1 n
n  hK
y = 0.00854x -2.57

0.001
n  2.58
0.0005
RAL insulation
hK  75.55
Kapton
0
1.5
1.6
1.7
1.8
1.9
2
2.1
Temperature, K
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
34
Contest
• Motivations of the program
• Cryostat NED
• Conventional insulation (Kapton) – Saclay sample
• Ceramic (innovative) insulation – KEK sample
• RAL conventional insulation – drum method
• Technical solutions investigation
• Conclusions
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
35
Technical solutions investigation
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
36
Technical solution investigation
Thermal blockades of the one side of the conductors
stack
0.9 mm
20 kN ≈10 MPa
Spacer
Vacuum grease – thermal blockade
G10 interlayer spacer
G10 interlayer spacer
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
37
Technical solution investigation
Test results
1800
Tb=1.9K
1600
1400
T-Tb, mK
1200
1000
1.9K-unins
1.9K-one side insul
800
1.9K G10
600
400
Tl
200
0
0
5
10
15
20
Power, mW/cm3
25
30
35
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
38
Contest
• Motivations of the program
• Cryostat NED
• Conventional insulation (Kapton) – Saclay sample
• Ceramic (innovative) insulation – KEK sample
• RAL conventional insulation – drum method
• Technical solution study
• Conclusions
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
39
Conclusion
•
For Nb3Sn technology magnets beam losses heat generation in cables
would be about 5 times higher then for NbTi technology
•
Temperature margin as 2.2 K is expected when the LHC convectional
electrical insulation is used to Nb3Sn cables
•
Innovative ceramic insulation seems to be very good solution for future
Nb3Sn magnets
•
Thermal conductivity of the RAL insulation material is 5 times lower
then Kapton with similar Kapitza resistance values – can be considered
as new conventional insulation
•
Yoke of magnet can strongly restrict heat transport from cables.
Application of the G10 interlayer spacers improve this process.
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
40
Thank you for your attention
J. Polinski, B. Baudouy -The NED heat transfer program at CEA
CEA Saclay, January 11th 2008
41