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NED heat transfer program at CEA Jaroslaw Polinski, Bertrand Baudouy CEA/ DAPNIA/SACM

Explore the thermal insulation program at CEA featuring innovative ceramic insulation, conventional Kapton insulation, and technical investigations for cryostats. Understand the motivations, experimental results, and conclusions of the program.

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NED heat transfer program at CEA Jaroslaw Polinski, Bertrand Baudouy CEA/ DAPNIA/SACM

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  1. NED heat transfer program at CEAJaroslaw Polinski, Bertrand BaudouyCEA/DAPNIA/SACM

  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

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. Helium phase diagram Cryostat NED • Cryostat scheme • (cooperation with WUT) Claudet bath principle

  9. Cryostat NED • Experimental setup at CEA Saclay

  10. Cryostat NED • Performance of the NED cryostat

  11. 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

  12. 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

  13. Conventional Kapton insulation • 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

  14. 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

  15. Conventional Kapton insulation • Saclay sample

  16. I II III IV V Conventional Kapton insulation • Test results – comparison with CERN results • Temperature of the heated conductor (conductor III) TIII For Q=10 mW/cm3 (NbTi) – DT≈50 mK For Q=50 mW/cm3 (Nb3Sn) – DT≈2.2K !!!

  17. Tb=2.0K I II III IV V Typically temperature characteristic for conductors adjoining to heated conductor Conventional Kapton insulation • Test results • Temperature of the conductors II and IV, adjoining to heated conductor TII TIV TIII<Tl TIII=Tl TIII>Tl Exemplary modeling results

  18. 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

  19. 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

  20. 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

  21. 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

  22. Ceramic (innovative) insulation KEK sample

  23. Ceramic (innovative) insulation • Test results For Q=10 mW/cm3 (NbTi) – DTmax<10 mK For Q=50 mW/cm3 (Nb3Sn) – DT<35 mK !!!

  24. 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

  25. Sample holder flange Support flange RAL insulation Construction of the drum test support

  26. RAL insulation • Drum setup • Theoretical Background of the Method (1/2) Ti A T1 Qs Constant T bath Heated volume 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 T2 Tb l

  27. RAL insulation • Drum setup • Theoretical Background of the Method (2/2) Since DT>>Tb it can be assumed that: And finally overall thermal resistance of the sample:

  28. Tested sheets RAL insulation • RAL insulationmaterial- fiberglass tape and epoxy resin Sheet surface photo

  29. Surface Roughness Tester Surface mathematical description H H h l W Thickness determination Surface roughness tester result RAL insulation Study of sheets surface area and thickness

  30. 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

  31. RAL insulation Test results and computation process, example forl=0.055 mm y = 0.5673x - 0.0013 where Evolution of the temperature difference across the sample with heat flux as a function of the bath temperature.

  32. RAL insulation Computation process

  33. RAL insulation Thermal conductivity, comparison with other materials

  34. RAL insulation Kapitza Resistance

  35. 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

  36. Technical solutions investigation

  37. 0.9 mm Spacer 20 kN ≈10 MPa Vacuum grease – thermal blockade G10 interlayer spacer Technical solution investigation Thermal blockades of the one side of the conductors stack G10 interlayer spacer

  38. Tl Technical solution investigation Test results

  39. 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

  40. 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.

  41. Thank you for your attention

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