Heat extraction through cable insulation and quench limits
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Transcript of Heat extraction through cable insulation and quench limits
The HiLumi LHC Design Study is included in the High Luminosity LHC project and is partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404.
Heat extraction through cable insulation
and quench limits
Pier Paolo Granieri, Rob van Weelderen, Lina Hincapié (CERN)
2nd Joint HiLumi LHC-LARP Annual MeetingINFN Frascati, 14-16 November 2012 (revised version 11/1/2013)
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Outline• Heat transfer through cable electrical
insulation: evolution• Experimental method• setup description• results
• Quench limits estimation• MQXF at 1.9 K bath temperature• vs. modeling results• vs. LHC magnets and MQXF at 4.2 K
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Heat transfer through cable electrical insulation: evolution
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Heat transfer through cable electrical insulation: evolution
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Heat transfer through cable electrical insulation: evolution
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Heat transfer through cable electrical insulation: evolution
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* unpublished measurements from D. Richter (5 SC heated cables, actual MQX cables)
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Heat transfer through cable electrical insulation: evolution
* unpublished measurements from D. Richter (5 SC heated cables, actual MQX cables)
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Experimental method• Sample: - 150 mm long rectangular stack
made of 6 alternating cables
• Cable: - CuNi10
- LHC cables geometry, MB inner layer
• T sensors: - AuFe0.07at%/Chromel differential
thermocouples
- in grooves in the central cable
- installed before impregnation
• Heating: - Joule heating along resistive strands
- steady-state
- different configurations (heated cables)
P.P. Granieri - Heat extraction and quench limits
P.P. Granieri - Heat extraction and quench limits
Experimental method
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• Insulation: - fiber glass sleeve
- vacuum impregn. resin: CTD-101
- thickness: 150 µm
• Cooling (transversal): - He II, 1.9 K
- He I, 4.2 K
• Pressure: 0 MPa
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Instrumented
cable
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Experimental results• Different position in the cable, Tbath, heating configuration
Tc (mid-plane, cable center)
Tc (mid-plane, cable edge)
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* 3 heated cables
Heat extraction from coil inner layer(cable center T)
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Heat extraction from coil inner layer(cable center T)
* 3 heated cables
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Quench limit estimation• Heat that must be (uniformly) deposited in the cable
until the cable center/edge reaches Tc:
P.P. Granieri - Heat extraction and quench limits
155 mW/cm3
198 mW/cm3 143 mW/cm3
247 mW/cm3
• MQXF
• 150 mm bore
(w/o µ-channels)
• 1.9 K constant bath T
• uniform heat deposit
88 mW/cm3
127 mW/cm3
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80 mW/cm3
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Quench limit estimation
• Comparison tests vs. model *, independently carried outCoil position(inner layer)
ΔT from exp. tests (mK)
ΔT from model *(mK)
Difference(%)
mid-plane 230-420 390 8
cable adjacent to pole
16-58 68 17
* previous talk from H. Allain
2.13 K
2.32 K
• Mid-plane and pole cable temperature for heat deposit in nominal conditions (peak of 3.78 mW/cm3)
1.96 K1.92 K
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Quench limit estimation• Comparison at nominal conditions in mid-plane
Magnet Estimated quench limit(mW/cm3)
Expected peak heat deposit (mW/cm3)
MB 46 0.6
MQXA 65 3.5
MQXB 60 / 75 3.5
MQXC 104 4
MQXF at 1.9 K(140 T/m)
155 4
MQXF at 4.2 K(80% Bss)
129 4
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Conclusions
• Numerical model of the experimental tests
• Thermal measurement of a short model coil
Perspectives
• Heat extraction through Nb3Sn insulation was measured
• worse than through LHC Nb-Ti insulation below a ΔT of 1.8 K (in the cable center), since the He II contribution is missing
• better than through Enhanced Nb-Ti insulation above a ΔT of 5.7 K (in the cable center), because kNb3Sn > KNb-Ti
3.7 K 6.4 K
scaled to magnet geometry
to be confirmed by a
dedicated test
• Heat extraction from the cable allows a first estimate of the quench limit: • MQXF mid-plane cable is the most critical: 155 mW/cm3, vs. 4 mW/cm3 expected
• MQXF-MQXC will have a quench limit 2 to 3 times those of MB-MQXA-MQXB