Abstract: Mixed refrigerants provide refrigeration at cryogenic temperatures with throttling cycles operating with a one-stage compressor. The refrigerants include noncondensable gases such as helium, neon, or hydrogen to increase the overall cooling capacity of a refrigeration system at the same refrigeration temperature which is attainable without such noncondensable gases. More refrigeration can be produced with existing systems at temperatures above the normal boiling point of nitrogen or argon by adding, for example, helium, than for refrigerant blends without helium. By increasing the return pressure value of the refrigeration cycle in relation to the molar percent of helium present in the refrigerant, a constant refrigeration temperature may be maintained which exhibits greater stability than prior systems operating at the same temperature without helium enrichment.

Abstract: An integral combination of expansion valve and evaporator in a cryostat using a single support member. The valve includes two flow orifices, one orifice being used primarily for steady-state operation and the other orifice being used only during cool-down. An actuator having a high coefficient of thermal expansion moves a needle positioned in the cool-down orifice such that a large orifice flow area at the start of cool-down is automatically and continuously reduced as the actuator temperature decreases as refrigerant is throttled through the orifice. Within a range of approximately 30 K from the desired steady-state evaporator temperature, the needle completely blocks the cool-down orifice. Then, refrigerant flows through the steady-state orifice which has a remotely adjustable needle. In the final stage of cool-down, the refrigerant system is entirely controlled by the steady-state orifice and its associated needle.

Abstract: A device for cryogenic refrigerating of an object below the triple point temperature of the cryogen. The device includes a housing in which is placed a porous plug. A liquid cryogen is supplied to one side of the plug at a pressure greater than the triple point of the cryogen. A pressure below the triple point is maintained on the other side of the porous plug. The cryogen flows through the plug and forms a solid on the supply side of the plug. The solid cryogen provides cooling by sublimation on a continuous basis to a cold station thermally coupled to the plug.