Open-cycle cryogenic refrigerator maintains temperature as low as 2K for periods up to six months. Designed to cool an infrared detector, refrigerator can be used in cooling Josephson-junction devices, magnetic bubble domains, and superconducting devices

Miller, C. G.

Stephens, J. B.

English

NASA Technical Reports Server

A new open-cycle cryogenic refrigerator maintains a 
temperature as low as 2 K for periods of up to 6 
months. Designed to cool an infrared (IR) detector, 
the refrigerator can be used in cooling other small 
devices, e.g., Josephson-junction devices, magnetic 
bubble domains, and superconducting devices. 
Permanent 
Vacuum 
Insulation
Pressure Vessel 
Dewar Jacket 
SHe 
Start:
2.76x10' N/rn 2 
(400 psia),
2.2 K
(3.8° A)
Vent Pressure
Regulator S
6 Months: 
(40 psia), Radiation-Shield 
Low-Pressure Side 
Counterflow 
Heat Exchanger 
Cavity 
Capillary 
Restrictor 
Refrigerator Schematic
High-Pressure Side 
IA Detector
August 1975	 B75-10181 
NASA TECH BRIEF 
• NASA Pasadena Office 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Briefprogram may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
A Two-Degree Kelvin Refrigerator 
The refrigerator is made up of a high-vacuum 
superinsulated Dewar with gas-cooled radiation 
shields, as shown in the illustration. The Dewar is 
filled with supercritical helium (SHe) to a pressure of 
2.76x10 6 N/m 2 (400 psia); the temperature of the SHe 
is above 2.2 K. 
The SHe flows through a counterfiow heat 
exchanger and discharges through a capillary tube 
restrictor with an inside diameter of 0.03 mm (0.001 
in.). At the end of this capillary, the helium undergoes 
a Joule-Thomson expansion into a low-pressure cavity 
(approximately 30 torr) to which the JR detector is 
connected. The expansion produces a mixture of gas 
and superfluid helium droplets. The droplets of He II 
percipitate onto the cavity wall where they evaporate, 
thus removing heat at 2 K or below from the detector. 
detector. 
The detector is thus cooled by the evaporating film 
of He II in the matrix. The gaseous helium (GHe) 
produced by this evaporation, along with the gas 
produced by the expansion, flows out through the 
low-pressure side of the counterfiow heat exchanger. 
It removes heat from the incoming stream of SHe. 
After leaving the heat exchanger, the GHe flows 
through the radiation shield of the Dewar, removing 
incoming radiation heat. From the shield the GHe 
flows through a pressure regulator which regulates 
vapor pressure in the detector-mount cavity, thus 
controlling the detector-mount temperature. The gas 
is then vented overboard through spacecraft attitude-
control jets. This clean, noncondensable gas jet is 
the noncontaminating, propulsive attitude-control 
system. 
(continued overleaf) 
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Government nor any person acting on behalf of the United States
	
will be free from privately owned rights. 
.
https://ntrs.nasa.gov/search.jsp?R=19750000181 2020-03-19T20:24:26+00:00Z
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: T5P75-10181
Patent status: 
This invention is owned by NASA, and a patent 
application has been filed. Inquiries concerning non-
exclusive or exclusive license for its commercial 
development should be addressed to: 
Patent Counsel 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Source: J. B. Stephens and C. G. Miller of 
Caltech/JPL 
(NPO-13459)
. 
Categories: 03 (Physical Sciences) 
06 (Mechanics) 
01 (Electronics - Components 
B75-10181
	 and Circuitry)


A two-degree Kelvin refrigerator

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