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Cryogenics for FPP S. Masi

Cryogenics for FPP S. Masi. Two inter-related issues: Cryogenic chain for the focal plane (final temperature 0.1K) Thermal system to radiatively cool the telescope (final Temperature as low as possible, hopefully 30K).

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Cryogenics for FPP S. Masi

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  1. Cryogenics for FPPS. Masi • Two inter-related issues: • Cryogenic chain for the focal plane (final temperature 0.1K) • Thermal system to radiatively cool the telescope (final Temperature as low as possible, hopefully 30K)

  2. Possible Dry Cryogenic Chain for FPP focal plane (Replicate Planck, 2 years lifetime) Radiative cooling to <50K With V-grooves FLOWN RAL Sorption Cooler Grenoble dilution (open cycle) Planck JT cooler (10M€) FLOWN FLOWN (16M€) 20K -> 4.5K P.S. 70W @ 300K Load 300 mW @ 20K Heat lift 14mW @4.5K 4.5K -> 0.1K P.S. - Load 2 mW @ 4.5K Heat lift 0.1uW @0.1K FLOWN (??M€)

  3. Possible Dry Cryogenic Chain for FPP focal plane (2 years) Partial replication of Planck, but simpler 20K system RAL PULSE TUBE Air-Liquide + CEA/SBT + Thales Cryogenics BV Grenoble dilution (open cycle) Planck JT cooler (10M€) SPACE QUALIFIED (??M€) FLOWN FLOWN (16M€) http://www.dta.airliquide.com/en/our-offer/space/equipments/cryo-refroidisseurs-tube-a-gaz-pulse-10-k-80-k.html 300K -> 20K P.S. 200W @ 300K Heat lift 5W @ 80K Heat lift 300mW @20K 20K -> 4.5K P.S. 70W @ 300K Load 300 mW @ 20K Heat lift 14mW @4.5K 4.5K -> 0.1K P.S. - Load 2 mW @ 4.5K Heat lift 0.1uW @0.1K

  4. Alternative Dry Cryogenic Chain for FPP focal plane (>4 years) RAL PULSE TUBE Air-Liquide + CEA/SBT + Thales Cryogenics BV Planck JT cooler Continuous ADR 4 stage (NASA-GSFC) 8 kg SPACE QUALIFIED (??M€) FLOWN (16M€) http://www.dta.airliquide.com/en/our-offer/space/equipments/cryo-refroidisseurs-tube-a-gaz-pulse-10-k-80-k.html TRL2-3 (??M€) 20K -> 4.5K P.S. 70W @ 300K Load 300 mW @ 20K Heat lift 14mW out @1.6K 300K -> 20K P.S. 200W @ 300K Heat lift 5W @ 80K Heat lift 300mW @20K 6K -> 0.1K P.S. - Load 35 mW @ 4.5K Heat lift 30 uW @0.1K

  5. Alternative Dry Cryogenic Chain for FPP focal plane (>4 years) RAL PULSE TUBE Planck JT cooler Air-Liquide + CEA/SBT + Thales Cryogenics BV FLOWN Continuous Dilution (Grenoble) 20K -> 4.5K SPACE QUALIFIED http://www.dta.airliquide.com/en/our-offer/space/equipments/cryo-refroidisseurs-tube-a-gaz-pulse-10-k-80-k.html Lab Tests done: TRL2-3 Sorption or JT Cooler 4.5K -> 1.6K 300K -> 20K P.S. 200W @ 300K Heat lift 5W @ 80K Heat lift 300mW @20K 1.6K -> 0.1K P.S. - Load ? mW @ 1.6K Heat lift 1uW @0.05K FLOWN, to be modified

  6. Radiative cooling of telescope • Would the telescope be thermally disconnected from the spacecraft, it would cool down radiatively: • A mass of 400 Kg of Al with a 3m2 surface blackbody radiating to cold space would get to 4 K in 44 days (more or less the cruise to L2). • The key is then to limit the heat transfer from the spacecraft and from the sun, earth, etc. • Planck did it very well using V.grooves to limit radiation, low conductivity struts and pipes. • We might be able to do better with FPP: • Little power dissipation from detectors • Lower number of pipes / Waveguides • Use of Passive Orbital Disconnecting Struts (PODS) • Use of part of the 20K pulse tube cooling power (or a second, dedicated one) Telescope 30K or less Conductive heat transfer Radiative heat transfer Spacecraft 300K

  7. Spitzer: Gamma-alumina/epoxy composite struts (yellow) : Better than fiberglass (COBE) and Titanium struts.

  8. or gamma-alumina

  9. Mass Budget • TBD

  10. Heat Load Budget • On the 0.1K stage: • Superconduncting wiring for 200 (?) SQUIDs multiplexing 2000 detectors, + first stage SQUIDs dissipation (2 mW) • Supports for focal plane assembly (cold plate, horns, filters) • On the 4K stage: • Wiring for readout electronics • Support system to 20K stage • Load from 0.1K cooler • On the 20K stage • Load from support system to 30-40K radiatively cooled stage • Load from 4K cooler (300 mW) • On the 40K stage • Load from support system to 300K stage • Residual radiative load through V.grooves • Load from 20K cooler (partial)

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