1

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

4-8

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

25

27Cryocoolers 18, edited by S.D. Miller and R.G. Ross, Jr.©¶International Cryocooler Conference, Inc., Boulder, CO, 2014

2

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

3

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

4

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

5

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

6

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.

4. Triqueneaux, S., Rocaboy, A., Duband, L., “Potential cooling chains for the NFI instruments of

XEUS,” Cryogenics, vol. 48, (2008), pp. 174-180.

5. Reed, J., Perkinson, M.C., D’Arrigo, P., Geelen, K., Hepburn, I., Brockley-Blatt, C., Duband L.,

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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9.

Astro-H Mission,” Proc. SPIE 7732, Space Telescopes and Instrumentation 2010: Ultraviolet to

Gamma Ray, (2010), p. 773212.

10. Luchier, N., Duval, J.M., Duband, L., Tirolien, T., “Performances of the 50 mK ADR/sorption

cooler,” Cryogenics, vol. 52, (2012), pp. 152–157.

11. Camus, P. et al., "Status of the Closed-Cycle Dilution Refrigerator Development for Space

Astrophysics", Journal of Low Temperature Physics, vol. 176, (2013), pp. 1-6.

12. Duval, J. M., Charles, I., Chassaing, C., Butterworth, J., Aigouy, G., and Mullié, J., “15 K pulse tube

design for ECHO mission,” Advances in Cryogenic Engineering, AIP Publishing, Melville, New

York, (2014), pp. 533-539.

13. Duval, J.M., Charles, I., Coynel, A., Gauthier, A., “Development of 15 K Pulse Tube Cold Fingers

for Space Applications at CEA/SBT,” Cryocoolers 16, International Cryocooler Conference,

Boulder CO, (2011), pp. 45-50.

14. Duval, J.M. et al., “Experimental results of 20K pulse tube cold Fingers for space applications,”

Cryocoolers 15, International Cryocooler Conference, Boulder CO, (2009), pp. 71-77.

15. Trollier, T., et al., “Design of a Miniature Pulse Tube Cryocooler for space applications,” Advances

in Cryogenic Engineering, Transactions of the Cryogenic Engineering Conference-CEC., Vol. 710.

No. 1. AIP Publishing, (2004), p. 1318.

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