Abstract: A multistage pulse tube cooler in which a portion of the heat from each successively lower-temperature pulse tube cooler is rejected to a heat sink other than the preceding higher-temperature pulse tube cooler, thus substantially improving the overall efficiency of the multistage cooler. Multistage pulse tube coolers of the prior art reject all the heat from each successively lower-temperature pulse tube cooler to the preceding higher-temperature pulse tube cooler, thus imposing a large cooling load on the higher-temperature pulse tube coolers which considerably reduces the overall efficiency of the cooler.

Abstract: A bi-directional Joule Thomson refrigerator is described, which is of simple construction at the cold end of the refrigerator. Compressed gas flowing in either direction through the Joule Thomson expander valve and becoming liquid, is captured in a container in direct continuous contact with the heat load. The Joule Thomson valve is responsive to the temperature of the working fluid near the valve, to vary the flow resistance through the valve so as to maintain a generally constant mass flow between the time that the refrigerator is first turned on and the fluid is warm, and the time when the refrigerator is near its coldest temperature and the fluid is cold. The valve is operated by differences in thermal coefficients of expansion of materials to squeeze and release a small tube which acts as the expander valve.

Abstract: A dual refrigeration system for cooling a sink device is described, which automatically thermally couples the cold refrigerator to the sink device while thermally isolating the warm refrigerator from the sink device. The system includes two gas gap heat switches that each thermally couples one of the refrigerators to the sink device, and a pair of sorption pumps that are coupled through tubes to the heat switches. When the first refrigerator (18) is operated and therfore cold, the first pump (50) which is thermally coupled thereto is also cooled and adsorbs gas to withdraw it from the second heat switch (44), to thereby thermally isolate the sink device (12) from the warm second refrigerator (26). With the second refrigerator being warm, the second pump (52) is also warm and desorbs gas, so the gas lies in the first switch (38), to close that switch and therefore thermally couple the cold first refrigerator (18) to the sink device.