ABSTRACT
The class of cryogenic devices to be examined is the so-called passive or static cooling systems. The efficiency of these systems has been described by their coefficient of performance. However, this system is simpler than a thermoelectric system since it consists of only one material and can be staged by simply shaping the conductor. Theoretically, a combination of thermoelectric and thermomagnetic systems could provide a small amount of cooling down to 70K, but such a system is not practical because of its large size and weight with respect to a mechanical system. An active cooling system has been developed by Aerojet Electronics Systems Company and is discussed below. In the split-Stirling system, reciprocating motion for the displacer is provided by a compact pneumatic drive wherein the sinusoidal pressure fluctuations generated by the compressor provide the necessary forces to drive the displacer back and forth in a properly timed relationship with the compressor.
