1. 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)

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

3. 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 Planck JT cooler 20K -> 4.5K P.S. 70W @ 300K Load 300 mW @ 20K Heat lift 14mW @4.5K Grenoble dilution (open cycle) Air-Liquide + CEA/SBT + Thales Cryogenics BV Possible Dry Cryogenic Chain for FPP focal plane (2 years) Partial replication of Planck, but simpler 20K system 4.5K -> 0.1K P.S. - Load 2 mW @ 4.5K Heat lift 0.1uW @0.1K FLOWN SPACE QUALIFIED (10M€) (16M€) RAL (??M€) PULSE TUBE

4. 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 Planck JT cooler 20K -> 4.5K P.S. 70W @ 300K Load 300 mW @ 20K Heat lift 14mW out @1.6K Continuous ADR 4 stage (NASA-GSFC) 8 kg Air-Liquide + CEA/SBT + Thales Cryogenics BV Alternative Dry Cryogenic Chain for FPP focal plane (>4 years) 6K -> 0.1K P.S. - Load 35 mW @ 4.5K Heat lift 30 uW @0.1K RAL TRL2-3 FLOWNSPACE QUALIFIED (16M€) (??M€) PULSE TUBE

5. 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 Planck JT cooler Continuous Dilution (Grenoble) Air-Liquide + CEA/SBT + Thales Cryogenics BV Alternative Dry Cryogenic Chain for FPP focal plane (>4 years) 1.6K -> 0.1K P.S. - Load ? mW @ 1.6K Heat lift 1uW @0.05K SPACE QUALIFIED FLOWN RAL Lab Tests done: TRL2-3 20K -> 4.5K Sorption or JT Cooler 4.5K -> 1.6K FLOWN, to be modified PULSE TUBE

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 3m 2 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) Spacecraft 300K Telescope 30K or less Radiative heat transfer Conductive heat transfer

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  W) –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)