Company Develops Clog-Free Cryostat
A NEW TYPE OF JOULE-THOMSON
CRYOSTAT developed under an Small Business Innovative Research (SBIR)
contract awarded by Kennedy Space Center features exclusive, anti-clogging
flow-regulation capabilities for custom-design applications. General
Pneumatics Corporation (GPC) of Phoenix, Arizona, is meeting a need
to provide very low-temperature cooling for infrared sensors, superconductors,
supercooled electronics, spacecraft, nuclear contamination detectors
and cryosurgery.
GPC company spokesman Woody Ellison said the Joule-Thomson cryostat
can operate continuously with gas contamination levels that would
quickly clog conventional cryostats. GPC cryostats employ a more
rugged and stable means of flow regulation than conventional cryostats,
and they can be equipped with a manual- or actuator-driven flow
adjustment, especially useful in developmental and laboratory applications.
NASA originally needed the innovation for vapor boil-off liquifiers
capable of extended operation for long periods without maintenance.
Ellison pointed out that GPC has also designed and produced custom
Joule-Thomson cryostats for several prospective applications, including
spacecraft, computer electronics, nuclear contamination detection
and counterproliferation, and cryosurgery.
The patented features have been incorporated in cryostats ranging
in cooling capacity from 0.25 watt to 50 watts. In simultaneous
testing with commercial grade nitrogen, GPC's cryostat demonstrated
continuous operation with contamination levels, which repeatedly
clogged conventional cryostats within six minutes. Under SBIR Phase
II, the cryostat design was extended to 50 watts with a cooling
capacity at 77 degrees Kelvin. NASA's Kennedy Space Center received
a design that was incorporated into a prototype closed-loop cryocooler
featuring a new oil-free, sealed high-pressure compressor and novel
closed-loop control scheme.
One development was a highly sophisticated adjustable two-stage
xenon/krypton cryostat assembly for Aerojet ESD. Also for Aerojet
ESD, GPC's research unit designed an anti-clogging cryostat to continuously
produce solid hydrogen at 10 degrees Kelvin. Another cryostat was
successfully tested at NASA's Jet Propulsion Laboratory in an experimental
80-degree Kelvin sensor cooler, which achieved a temperature stability
three orders of magnitude better than conventional cryostats. For
CryoGen, GPC's research unit provided a prototype anti-clogging
cryostat for a closed-cycle cryosurgery system.
A recent development for the U.S. Department of Energy's Remote
Sensing Laboratory, operated by Bechtel Nevada, is a common-module-size
(0.204-inch bore, 2.62-inch-deep coldwell), self-regulating cryostat,
which produces up to 16 watts of refrigeration for several hours
using 3,000 pounds per square inch of argon to cool an HPGe gamma-ray
detector to below 100 degrees Kelvin.
Global security is an important commercial application. GPC's
cryostat innovation is a key part in the development of more portable
high-purity germanium gamma-ray spectrometers. These spectrometers
are necessary to discern among radionuclides in medical, fuel, weapon
and waste materials. The ability to monitor nuclear materials, verify
possible hazards and develop counterproliferation tactics has become
increasingly crucial to global security.
The Joule-Thomson effect is the change in temperature that occurs
when a gas expands into a region of lower pressure. A decrease in
temperature takes place when gas expands through a throttling device.
A gas must be below its inversion temperature. If above, it gains
heat on expansion.
For more information, contact Tom Gould at Kennedy Space Center.
Call: 407/867-6238, Fax: 407/867-2050, E-mail: Thomas.Gould-1@
kmail.ksc.nasa.gov
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