15k pulse tube cooler for space missions · 2017-11-16 · thomson cooler. the final 50mk stage can...
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ABSTRACT
Air Liquide is working with ESA, CEA and Thales Cryogenics to design, manufacture and
test a 15K Pulse Tube cooler system. This cooler is particularly adapted to the pre-cooling needs
of cryogenic chains designed to reach 0.1-0.05K for scientific space missions. For the present
project, the required cooler temperature is from 15 to 18K with a cooling power between 0.1 and
0.4 watts. The overall electrical power budget is less than 300W (without the electronics) with a
288K rejection temperature. Significant cooling power at an intermediate temperature (typically
80K – 120K) is also available.
Particular attention is therefore paid to optimizing overall system efficiency. To achieve this
low temperature, two cold fingers working in parallel have been integrated on one common
warm flange and they are connected to one specially developed high power compressor (240W
PV power).
The presented work concerns the 15K cooler design and the expected performance in both
analytical simulations and the laboratory tests.
This Pulse Tube Cooler addresses the requirements of space missions where temperatures
lower than 20K, cooling power higher than 0.1W, extended continuous operating life time (>5
years), compactness, low mass, and low micro vibration levels are critical.
INTRODUCTION
Air Liquide has been developing pulse tube cryocoolers for space applications since the turn
of the century. The Large Pulse Tube Cooler (LPTC: 3-7W cooling @ 50-80K) is currently in
the final stages of qualification for the French CSO mission and will also equip the IRS and FCI
instruments of the European Meteosat Third Generation satellites.1
The Miniature Pulse Tube
Cooler (MPTC) which was designed to provide 1.5W of cooling at 80K has recently been re-
optimized for high efficiency, low power operation at temperatures in the range 150-200K.2
Air
Liquide also developed and manufactured the 100mK dilution cooler for the Planck CMB survey
mission launched in 2009.3
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15K Pulse Tube Cooler for Space Missions
C. Chassaing1
, J. Butterworth1
, G. Aigouy1
, J.M. Duval 2
, I. Charles
2
T. Rijks 3
, J.Mullié 3
, M. Linder 4
1
Air Liquide, Sassenage, France
2
Univ. Grenoble Alpes, CEA INAC-SBT, Grenoble, France
3
Thales Cryogenics BV, Eindhoven, NL
4
European Space Agency (ESA), Noordwijk, NL
This is typically performed using a combination of several cooling into the mil ikelvin region.l
sIn recent years a number of scientific missions ha been proposed which require detector
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27Cryocoolers 18, edited by S.D. Miller and R.G. Ross, Jr.©¶International Cryocooler Conference, Inc., Boulder, CO, 2014
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passive and/or active cooling stages, each stage providing precooling for the following stage and
often additional cooling power for radiation shields and interception of conductive heat loads.
Several cooling chains currently envisaged for future X-ray observatories including SXS
Thomson cooler. The final 50mK stage can be provided by a multi-stage Adiabatic
Demagnetization Refrigerator (ADR) 9
, a hybrid 3
He sorption/ADR10
or a closed cycle dilution
refrigerator.11
Similar cooling chains will also be required for the proposed COrE and PRISM
cosmic microwave background survey missions.
The 15K pulse tube cooler currently under development by Air Liquide, in collaboration
with CEA/SBT and Thales Cryogenics BV, was originally intended to address the 3
He JT
precooling requirements of the XMS instrument for the IXO mission (predecessor of ATHENA),
also providing additional shield cooling capabilities at 15K and below 120K. It was considered
as a potential candidate for the proposed EChO mission12
, and is currently under consideration
for a European cooling chain to be developed under ESA funding, which could then be
implemented for the X-IFU instrument aboard ATHENA.
15K PULSE TUBE COOLER DESCRIPTION
Following initial trade-off and breadboarding phases13
, the selected geometry employs a
single stage 15K pulse tube cold finger which is thermally intercepted by a second cold finger at
a temperature of 100-120K as shown in Figure 1. The cold fingers are mounted on a common
warm flange so that only a single mechanical and warm thermal interface is required. Both cold
fingers are coupled to a single large compressor (maxi-compressor), as shown in Figure 2,
currently under development by Thales Cryogenics.
This configuration makes extensive use of existing heritage including the Large Pulse Tube
Cooler (LPTC), for the 100-120K stage, and the Engineering Model 20-50K pulse tube cooler14
already developed under ESA GSTP funding for the 15K stage.
The LPTC cold finger, although retaining its original mechanical design, has been re-
optimized to operate at the same pressure and frequency as the 15K cold finger. The pressure
wave phase shift is generated using a slightly modified LPTC inertance/buffer design.
For low temperature pulse tube operation it is difficult to obtain the optimal phase shift
parameters using passive means, such as an inertance tube with or without double injection, and
Figure 1. 15K 2-stage cold head showing thermal link and launch support assemblies
Common warm
flange
Common launch
support
1st stage cold
interface
(100-120K)
Thermal link
assembly
2nd
stage thermal
interface (15K)
Warm thermal
interface
Warm mechanical
interface
aboard ASTRO-H (JAXA) and X-IFU on ATHENA (proposed for the ESA Cosmic Vision L2
mission) include a mechanical 15K cooling stage which is used to precool a helium-3 Joule-
26 Cryocoolers for 4-40 K Space & Military Applications 2828 CRYOCOOLERS FOR 4-40 K SPACE & MILITARY APPLICATIONS
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into the cold finger and is therefore not subject to the same thermal and thermomechanical
constraints that can lead to limited lifetime and side-load sensitivity of the cold finger as well as
the generation of high exported vibration levels. The compressor already developed in the
framework of the Miniature Pulse Tube cooler15
(ESA, Air Liquide, TCBV, CEA/SBT) is well
suited to this purpose. It consists of a dual opposed piston, flexure bearing design similar to the
main large compressor, with long lifetime and very low exported vibration.
A new 300W large swept volume maxi-compressor is under development for this cooler,
largely based on the heritage of the LPTC and MPTC designs as well as that of terrestrial coolers
developed by Thales Cryogenics. An engineering model of this compressor is being manufac-
tured and will be available by November 2014.
A proposed integration architecture for the cooler assembly is shown in Figure 3, including
the cold head, compressor, active phase shifter and inertance/buffer sub-assemblies. The Critical
ready for testing by the end of 2014.
Common warm
flange
LPTC cold finger
1st stage thermal
interface
2nd stage thermal
interface
Buffer
Figure 2. Schematic of the 15K Pulse Tube Cooler
Thermal link
Inertance
Active phase
shifter
Common
Maxi-Compressor
15K cold finger
Intercept
Figure 3. Proposed integration architecture for 15K PT cooler system
Common
Maxi-Compressor
Inertance/buffer
assembly
Active phase
shifter
Cold Head
Assembly
it has been found preferable to use an active phase shifter connected to the warm end of the
pulsation tube of the second stage cold finger. This is essentially a small compressor working in
reverse (the pistons are excited by the pressure wave) and is analogous to the active displacer of
a stirling cooler. Unlike a stirling displacer however, the active phase shifter is not integrated
Design eview has been passed in early 2014 and an engineering model will be assembled and R
2715K PULSE TUBE COOLER FOR SPACE MISSIONS 292915K PULSE TUBE COOLER FOR SPACE MISSIONS
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connected in parallel to a common split pipe.
For testing purposes, the 1st
stage and 2nd
stage cold fingers were mounted separately in the
cryostat and connected together via a 250mm long thermal link as shown in Figures 4 and 5. This
represents a much lower thermal conductance than that foreseen for the integrated design shown
in Figure 1.
Figure 6 shows the cooling power obtained at 15K as a function of the total input electrical
power to the compressor. 300mW of cooling power is achieved at the 2nd
stage for 290W
electrical power. It can be seen that for compressor powers up to 350W there is no sign of
saturation, suggesting that higher powers can be achieved if a sufficient pressure wave can be
generated.
Figure 5. Coupled 15K + LPTC precooler thermal link
1st stage
LPTC cold finger
Cu braid heat link 2nd stage
15K cold finger
100-120K
intercept
Figure 4. Coupled 15K + LPTC precooler test setup
1st stage
LPTC cold finger
1st stage
inertance
2nd stage
Active phase shifter
2nd stage
15K cold finger
GM cooler - not
used during this
test
Dual LPT9710
compressors
(vertically stacked)
250mm
PERFORMANCE ESTIMATIONS AND PRELIMINARY TESTS
• 1st
stage (80-120K): Re-optimized EM LPTC cold finger with passive phase shifter
• 2nd
stage (15K): EM 20-50K pulse tube cold finger with active phase shifter
Owing to the long length and relatively small cross section of the thermal link used for these
measurements, a very large temperature difference of ~30K was observed between the LPTC
cold tip and the 2nd
stage intercept. It is known from earlier measurements that the intercept
temperature has very little impact on 2nd
stage performance for values below 120K. With a 1.2W
additional “user” heat load on the 1st
stage interface, we obtained a 1st
stage temperature of 80K
resulting in an intercept temperature of 110K with 290W electrical power and the second stage at
15K. For the thermal link design which will equip the EM cooler (see Figure 1), the thermal
verify their behavior when driven by a single common compressor:
A test campaign has been performed using two existing engineering model cold fingers to
The large volume maxi-compressor is represented by Thales LPT9710 compressors two
28 Cryocoolers for 4-40 K Space & Military Applications 3030 CRYOCOOLERS FOR 4-40 K SPACE & MILITARY APPLICATIONS
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Owing to the long length and relatively small cross section of the thermal link used for these
measurements, a very large temperature difference of ~30K was observed between the LPTC
cold tip and the 2nd
temperature has very little impact on 2nd
additional “user” heat load on the 1st
stage interface, we obtained a 1st
stage temperature of 80K
resulting in an intercept temperature of 110K with 290W electrical power and the second stage at
gradient has been calculated to be lower than 5K, enabling the 1st
stage temperature to be
increased to ~110K without any decrease in 2nd
stage performance. This corresponds to an
increase of more than 3W in available 1st
stage cooling power.
Figure 7 shows the dependence of the measured re-optimized LPTC cooling power together
with the estimated heat load from the intercept of the 2nd
stage cold finger, both as a function of
temperature for 260W electrical power. The cooling power available to the user for shield
cooling etc is the difference between these two contributions (taking into account a temperature
difference across the thermal link of ~5K). It is therefore expected that the net cooling power
available to the user at this stage will be greater that 4 - 5W @ 100 – 110K for <300W total
electrical input power.
CONCLUSION
representative of a future flight design is being manufactured. Initial tests using existing
Figure 6. 2nd stage cooling power @ 15K as a function of compressor input electrical power
Figure 7. Breakdown of 1
st
stage cooling power
stage performance for values below 120K. With a 1.2W
stage intercept. It is known from earlier measurements that the intercept
15 K. For the thermal link design that will equip the EM cooler (see Figure 1), the thermal
A 2-stage 15K pulse tube cooler system has been designed and an engineering model ,
2915K PULSE TUBE COOLER FOR SPACE MISSIONS 313115K PULSE TUBE COOLER FOR SPACE MISSIONS
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REFERENCES
1. Butterworth, J., Aigouy, G., Chassaing, C , Debray, B., Huguet, A., “Pulse tube coolers for Meteosat
third generation,” Advances in Cryogenic Engineering, AIP Publishing, Melville, New York, (2014),
pp. 520-524.
2. Chassaing, C., Butterworth, J., Aigouy, G., Daniel, C., Crespin, M., Duvivier, E., “150K - 200K
miniature pulse tube cooler for micro satellites,” Advances in Cryogenic Engineering, AIP
Publishing, Melville, New York, (2014), pp. 525-532.
3. Triqueneaux, S., Sentis, L.1, Camus, Ph., Benoit, A., Guyot, G., “Design and performance of the
dilution cooler system for the Planck mission,” Cryogenics, vol. 46, (2006), pp. 288–297.
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Bradshaw, T., “300 mK and 50 mK cooling systems for long-life space applications”, Cryogenics,
vol. 48, (2008), pp. 181-188.
6. Fujimoto, R. et al., “Cooling system for the soft X-ray spectrometer onboard Astro-H,” Cryogenics,
vol. 50, (2010), pp. 488-493.
7. Barret, D. et al., “The Hot and Energetic Universe: The X-ray Integral Field Unit (X-IFU) for
Athena+,” ArXiv e-prints, 1308.6784 [astro-ph.IM], (2013).
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cooler,” Cryogenics, vol. 52, (2012), pp. 152–157.
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design for ECHO mission,” Advances in Cryogenic Engineering, AIP Publishing, Melville, New
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for Space Applications at CEA/SBT,” Cryocoolers 16, International Cryocooler Conference,
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hardware show that the cooler will be able to generate 300mW @ 15K + 5W @ ~100K with
300W electrical input power. It is foreseen to further optimize the performance in a dedicated
engineering model to reduce the specific power consumption and to increase the maximum
available cooling power at 15K.
The engineering model will be assembled and ready for testing by the end of 2014 with a
comprehensive test sequence planned for early 2015.
ACKNOWLEDGMENT
We acknowledge the financial and technical support of the European Space Research and
Technology Centre (European Space Agency/ESTEC, Contract n° 4200023025/10/NL/AF).
Shirron, P.J. et al., “Design of a 3-Stage ADR for the Soft X-Ray Spectrometer Instrument on the
Cryogenics,
vol. 52, (2012), pp. 145–151.
Duband , L., Duval , J., Luchier , N. , Prouve , T. , “SPICA sub-Kelvin cryogenic chains,”
30 Cryocoolers for 4-40 K Space & Military Applications 3232 CRYOCOOLERS FOR 4-40 K SPACE & MILITARY APPLICATIONS