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)

Planck JT cooler

20K -> 4.5K

P.S. 70W @ 300K

Load 300 mW @ 20KHeat 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 @ 4.5KHeat lift 0.1uW @0.1K

FLOWN FLOWN

FLOWN

(10M€)(16M€)

RAL

(??M€)

Radiative cooling to <50KWith V-grooves

FLOWN

Sorption Cooler

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 @ 80KHeat lift 300mW @20K

Planck JT cooler

20K -> 4.5K

P.S. 70W @ 300K

Load 300 mW @ 20KHeat 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 @ 4.5KHeat lift 0.1uW @0.1K

FLOWN FLOWNSPACE QUALIFIED (10M€)(16M€)

RAL

(??M€)

PULSE TUBE

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 @ 80KHeat lift 300mW @20K

Planck JT cooler

20K -> 4.5K

P.S. 70W @ 300K

Load 300 mW @ 20KHeat 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 @ 4.5KHeat lift 30 uW @0.1K

RAL

TRL2-3

FLOWNSPACE QUALIFIED (16M€)(??M€)

(??M€)

PULSE TUBE

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 @ 80KHeat 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 @ 1.6KHeat lift 1uW @0.05K

SPACE QUALIFIED

FLOWN

RAL

Lab Tests done: TRL2-3

20K -> 4.5K

Sorption or JT Cooler4.5K -> 1.6K

FLOWN, to be modified

PULSE TUBE

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)

Spacecraft 300K

Telescope 30K or less

Radiative heat transfer

Conductive heat transfer

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

or gamma-alumina

Mass Budget

• TBD

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)