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Heat extraction through cable insulation and quench limits. Pier Paolo Granieri, Rob van Weelderen, Lina Hincapié (CERN) 2 nd Joint HiLumi LHC-LARP Annual Meeting INFN Frascati , 14-16 November 2012 (revised version 11/1/2013). Outline. - PowerPoint PPT Presentation
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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)
P.P. Granieri - Heat extraction and quench limits 2
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
P.P. Granieri - Heat extraction and quench limits 3
Heat transfer through cable electrical insulation: evolution
P.P. Granieri - Heat extraction and quench limits 4
Heat transfer through cable electrical insulation: evolution
P.P. Granieri - Heat extraction and quench limits 5
Heat transfer through cable electrical insulation: evolution
P.P. Granieri - Heat extraction and quench limits 6
Heat transfer through cable electrical insulation: evolution
*
*
*
* unpublished measurements from D. Richter (5 SC heated cables, actual MQX cables)
P.P. Granieri - Heat extraction and quench limits 7
Heat transfer through cable electrical insulation: evolution
* unpublished measurements from D. Richter (5 SC heated cables, actual MQX cables)
*
*
*
8
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
9
• 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
1
2
3
4
5
6
Instrumented
cable
P.P. Granieri - Heat extraction and quench limits 10
Experimental results• Different position in the cable, Tbath, heating configuration
Tc (mid-plane, cable center)
Tc (mid-plane, cable edge)
P.P. Granieri - Heat extraction and quench limits 11
* 3 heated cables
Heat extraction from coil inner layer(cable center T)
P.P. Granieri - Heat extraction and quench limits 12
Heat extraction from coil inner layer(cable center T)
* 3 heated cables
13
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
39
188
80 mW/cm3
106
P.P. Granieri - Heat extraction and quench limits 14
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
P.P. Granieri - Heat extraction and quench limits 15
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
P.P. Granieri - Heat extraction and quench limits 16
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