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Cryogenics for B-Pol

Cryogenics for B-Pol. S. Masi, reporting from F.X. Desert L. Piccirillo …. Use SAMPAN as a baseline, and look for improvements/variations. Bpol Cryogenics : main drivers. Provide cooling of the detectors Additional cooling for other parts of the detection chain

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Cryogenics for B-Pol

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  1. Cryogenics for B-Pol S. Masi, reporting from F.X. Desert L. Piccirillo …. Use SAMPAN as a baseline, and look for improvements/variations

  2. FXD BPol Cryogenics Roma Bpol Cryogenics : main drivers • Provide cooling of the detectors • Additional cooling for other parts of the detection chain • Stable environment for the optics & baffle • Accomplished by a succession of thermal stages • Shields • Passive cooling: V-grooves • Main Cryostat: to reach T < 8 K to lower the optical background • SubKelvin cooler • For a total lifetime of 2.5 years + margins François-Xavier Désert (LAOG) Grenoble

  3. FXD BPol Cryogenics Roma Cryogenic Architecture The satellite architecture is built around the cryogenics The cold payload needs to be protected from the sun and the SVM with thermal screens, with incidences up to +/- 90° from the satellite axis, and at the same time the cooling philosophy based on passive first stages requires a large factor of view of the payload to the space. Examples drawn from Sampan Phase 0 Study CNRS: F. Bouchet (Sampan leader) M. Piat, N. Ponthieu, M. Bucher, A. Benoit, Ph. Camus CNES/PASO: J. Michaud (Study leader) Alcatel Alenia Space: Ph. Desmet Air Liquide: S. Triqueneaux Shield, V-grooves, and cryostat = PLM cylindrical SVM

  4. FXD BPol Cryogenics Roma Constraints • Cryogenic needs : • 1µW @ 150mK (Integrated power between 2 K & 150 mK) or a bit less power @ 100 mK. • 800µW @ 2K: Electronics + optics • 12mW @ 8K: Electronics + optics • Launch constraints • Operations before launch • withstanding vibrations • Mass/Volume/Cryogenic lifetime • Active or passive regulations of thermal stages

  5. FXD BPol Cryogenics Roma Constraints • Cryogenic needs : • 1µW @ 150mK (Integrated power between 2 K & 150 mK) or a bit less power @ 100 mK. • 800µW @ 2K: Electronics + optics • 12mW @ 8K: Electronics + optics • Launch constraints • Operations before launch • withstanding vibrations • Mass/Volume/Cryogenic lifetime • Active or passive regulations of thermal stages These numbers depend strongly on the size of the focal plane: Variations have a huge impact

  6. FXD BPol Cryogenics Roma Thermal architecture : concept 1SAMPAN V-grooves to keep the cryostat shell at 40K. Like Planck, but with grooves folded forward, to allow operation from antisun to 90 deg from sun

  7. Schematic Drawing of the Cryostat Note that the SAMPAN telescope is small (30 cm) !! If you increase the size, the cryostat will grow a lot

  8. Main Results for the Cryostat • Both cryostats have similar dimensions (helium slightly larger) • Overall mass for LHe / SH2 : LHe about 3 times heavier • Mass of LHe strongly depends on last V-Groove temperature (80K => + 60 kg on the overall mass) • Type of detector (High-Imp or TES) has a reduced impact on overall mass (< 10 %) • Heritage from ISO, Herschel, Studies for JWST • Cryogenic machines could be considered as an intermediate stage: e.g. a 4 K improved version of Planck HFI cooler. But otherwise Sorption machines (no vibrations) are heavy/voluminous and not considered further

  9. SAMPAN SubKelvin Cooler : • - Heritage from Planck HFI dilution cooler • - Modifications: • - more power at 100 - 200 mK : 800nW (200nW for Planck) • - start from an initial stage at 8 K (if SH2 retained) instead of 4.5 K • - store He isotopes into the main cryostat (no more high pressure tanks) • - Develop closed cycle dilution to increase lifetime and reduce 3He cost. But not off-the-shelf yet. • - ADR is less developed in Europe • - 300 mK (JT of 3He) is not continuous and reduces sensitivity Planck “demonstrator”

  10. Other option : ADR PROs • more power at 100 mK (5 mW) – needed if we widen the focal plan to accomodate lower f • Intrinsically gravity independent • Tested on balloons and rocket flights (McCammon) CONs • Cycling and Power required • Safety issues for superconducting magnet (but see AMS)

  11. European Expertise • CRTBT, RAL, ALCATEL, Air Liquide – see Planck • Other possibilities: • in Italy Galileo, ALENIA, RIAL … • In Germany Vericold, MAN …

  12. FXD BPol Cryogenics Roma

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