Cryogenics for B-PolS. Masi, reporting from
F.X. DesertL. Piccirillo
….
Use SAMPAN as a baseline, and look for improvements/variations
FXD BPol Cryogenics Roma30/03/2007 p. 2
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
FXD BPol Cryogenics Roma30/03/2007 p. 3
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.
Shield, V-grooves, and cryostat = PLM
cylindrical SVM
Examples drawn from Sampan Phase 0 StudyCNRS: F. Bouchet (Sampan leader) M. Piat, N. Ponthieu, M. Bucher, A. Benoit, Ph.
Camus
CNES/PASO: J. Michaud (Study leader) Alcatel Alenia Space: Ph. DesmetAir Liquide: S. Triqueneaux
FXD BPol Cryogenics Roma30/03/2007 p. 4
Constraints
Cryogenic needs :1µW @ 150mK (Integrated power between 2 K & 150 mK) or a bit less power @ 100 mK.800µW @ 2K: Electronics + optics12mW @ 8K: Electronics + optics
Launch constraintsOperations before launchwithstanding vibrations
Mass/Volume/Cryogenic lifetimeActive or passive regulations of thermal stages
FXD BPol Cryogenics Roma30/03/2007 p. 5
Constraints
Cryogenic needs :1µW @ 150mK (Integrated power between 2 K & 150 mK) or a bit less power @ 100 mK.800µW @ 2K: Electronics + optics12mW @ 8K: Electronics + optics
Launch constraintsOperations before launchwithstanding vibrations
Mass/Volume/Cryogenic lifetimeActive or passive regulations of thermal stages
These numbers depend strongly on
the size of the focal plane:Variations have a huge impact
FXD BPol Cryogenics Roma30/03/2007 p. 6
Thermal architecture : concept 1SAMPANSAMPAN
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
Schematic Drawing of the Cryostat
Dilution
300 mm
350 mm
350 mm
540 mm
20°
< 5
00 m
K2
K
< 8 K
2K
< 8K
320 mm
phi int réservoir : 500 mm
L2
FPhau
teu
r ré
serv
oir
: 1
200
mm
L1
Cryostat: enceinte au vide
2K
Structure 100K
SVM
SH2
GHeGHe DCCU
100mK
2K
8K
Note that the SAMPAN telescope is small (30 cm) !!If you increase the size, the cryostat will grow a lot
Main Results for the Cryostat
Both cryostats have similar dimensions (helium slightly larger)Overall mass for LHe / SH2 : LHe about 3 times heavierMass 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 JWSTCryogenic 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
Cryostat Param
Nb of shields (CVV -> Tank)
Inner Temp
(K)
CVV Temp
(K)
Tank Inner P
(Pa)
Cryogen flow
(mg/s)
Cryogen* Overall Tank IDCVV OD
CVV height
SH2 2 8 43 15 0,21 21 109 0,5 0,92 1,71LHe 3 2 34 3,1 0,74 88 352 0,5 1,26 1,66
* Main Cryogen only
Main Dim(m)
Mass(kg)
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”
Other option : ADRPROs more power at 100 mK (5 W) – 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)
European Expertise
CRTBT, RAL, ALCATEL, Air Liquide – see Planck
Other possibilities: in Italy Galileo, ALENIA, RIAL … In Germany Vericold, MAN …
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