Abstract: A cryostat (10') with a heat exchanger (13'); a valve (25') for controlling the flow of fluid through said heat exchanger (13'); and a snap disk (30') for actuating the valve (25'). In a specific embodiment, the snap disk (30') is constructed of at least two different materials (32', 34'), each having a different coefficient of thermal expansion. The snap disk (30') is mounted upon an orifice block (38') and coupled to a needle valve (25') by a connecting rod (40'). The needle valve (25') engages an orifice (16') in the orifice block (38'). The orifice (16') is in communication with the tubing (14') of a heat exchanger (13') via a channel (44') in the orifice block (38'). The geometry of the snap disk (30') is such that when the disk changes state, it snaps due to the thermal properties thereof. This ensures fast response with abrupt closure characteristics and considerable travel. In addition, the snap disk (30') allows for a simplified cryostat design with minimal weight and cost.

Abstract: A demand-flow Joule-Thomson cryostat 10' adapted for use with multiple coolants uses a replaceable coolant supply reservoir 21' to fill a coolant flow control bellows 17' within the cryostat with the same coolant used to provide refrigeration to the thermal load 15'. Upon termination of the cooling cycle, the bellows 17' is drained of coolant and thus prepared for operation from a different coolant supply 21' that may contain a different cryogen.

Abstract: An airborne cryogenic cooling system in which a first cryogenic material located within an on-board container is cooled to the solid state prior to launch a remotely located second cryogen conduited to the container. Immediately prior to becoming airborne connection is broken to the second cryogen and on-board cooling is achieved by venting the container to space environment causing sublimation of the solid first cryogenic, or, alternatively, the container may be left sealed and cooling results from triple-point transition of the solid cryogen.

Abstract: A dewar (20) useful in rapidly cooling a sensor (28) supported thereon includes a bore tube assembly having a cylindrical dewar bore tube (22) with an end cap (24) at one end to close the bore tube (22). The bore tube assembly is cooled by directing a stream of coolant at the interior of the end cap (24). The sensor (28) is mounted directly to the exterior surface of the end cap (24). A cold shield (34) partially encloses the sensor (28). A cold shield support bracket (38) mounts the cold shield (34) to the cylindrical side walls of the dewar bore tube (22) at a mounting location (36) axially displaced from the end cap (24) and therefore less effectively cooled than the end cap (24), so that heat is extracted from the support bracket (38) and the cold shield (34) less rapidly than from the sensor (28). From an uncooled starting condition, the sensor (28) is cooled to its operating temperature, and the cold shield (34) is cooled to its operating temperature, in about the same time.

Abstract: A two-stage Joule-Thomson cryostat (10) has a first-stage cryostat (12) with a helical-coil heat exchanger (14) and and isenthalpic gas expansion orifice (20) that discharges a mixture of cooled gas and cryogenic liquid into a liquid cryogen plenum (26). A second-stage cryostat (30) with a helical coil heat exchanger (32), wound to a larger diameter than the first-stage heat exchanger coil (14), is wound around and in thermal contact with the liquid cryogen plenum (26). This arrangement achieves a high degree of interstage heat transfer and cooling of the gas flowing in the second-stage heat exchanger coil (32) by the liquid cryogen in the first-stage liquid cryogen plenum (26). In operation, a gas flow management system (60), designed for rapid cooldown, initially passes a first gas of high specific refrigerating capacity through both stages (12 and 30).

Abstract: A refrigerating device (34 or 46) is formed using a refrigerating unit (10) having a hot end (32) at which heat is transferred to a heat sink (22), a cold end (30) at which heat is transferred from a cooling load (28) to the unit (10), a first junction (14) of a material (16) carrying electrical current in a nonsuperconducting mode to a material (12) carrying electrical current in a superconducting mode nearest the hot end (32), a second junction (18) of a material (12) carrying electrical current in a superconducting mode to a material (20) carrying electrical current in a nonsuperconducting mode nearest the cold end (30), and an electrical current source (24) that forces a flow of electrical current in the direction from the first junction (14) toward the second junction (18). As the electrical current flows, heat is transferred from the cooling load (28) into the cold end (30), and expelled to the heat sink (22) at the hot end (32).

Abstract: A practical cryogenic Peltier cooler is devised by replacing one of the semiconducting elements in a conventional peltier cooler with an element comprised of bulk, or thin film superconducting material. In the preferred embodiment, a rare-earth, a barium copper oxide superconductor of the form Yb.sub.a Cu.sub.3 O.sub.x is utilized. The superconducing elements are placed in an alternating series with semiconducting elements comprised of bismuth telluride of the form Bi.sub.2 Te.sub.3 (n-type). Performance may be improved in an alternative embodiment by utilizing instead a bismuth antimony semiconductor of the form Bi.sub.85 Sb.sub.15 (n-type). As a result, cryogenic Peltier coolers can be devised with useful refrigeration capacities and stable cold temperatures of 65-80 degrees Kelvin and below, while heat sinked to a higher temperature.