A cryogenic refrigerator includes a regenerative heat exchanger material in thermal contact with a working gas including a tin-antimony (SnSb) alloy or a tin-gallium (SnGa) alloy in at least one cooling stage. The regenerative heat exchanger material can include an SnSb-M alloy, with M including at least one element selected from the group consisting of Bi, Ag, Ge, Cu, La, Mg, Mn, Nd, Ni, Pd, Pt, K, Rh, Sm, Se, S, Y, Fe, In, Al, Ce, Dy, Cd, Ti, Au, P, Pr, Yb and Zn. The cryogenic refrigerator can include a Gifford-McMahon refrigerator, a pulse tube refrigerator, or a Stirling refrigerator. A cryopump includes cryopanels adapted to condense or adsorb gases and a cryogenic refrigerator.

Embodiments are directed to a heat pump element comprising: a thin-film polymer or ceramic material within a range of 0.1 microns-100 microns thickness, and electrodes coupled to both sides of the thin-film material to form an electroded active thin-film material, wherein the thin-film material is separated by, and in intimate contact with, a heat transfer fluid in channels within a range of 10 microns-10 millimeters thickness, in which the fluid is capable of being translated back and forth through the element by an imposed pressure field.

Provided is a group of rare-earth regenerator material particles having an average particle size of 0.01 to 3 mm, wherein the proportion of particles having a ratio of a long diameter to a short diameter of 2 or less is 90% or more by number, and the proportion of particles having a depressed portion having a length of 1/10 to of a circumferential length on a particle surface is 30% or more by number. By forming the depressed portion on the surface of the regenerator material particles, it is possible to increase permeability of an operating medium gas and a contact surface area with the operating medium gas.

Disclosed is a sub-Kelvin temperature zone refrigeration mechanism. The sub-Kelvin temperature zone refrigeration mechanism includes a pulse tube refrigeration unit, first pre-cooling heat exchangers, a throttling refrigeration unit, second pre-cooling heat exchangers, an adsorption refrigeration unit, a third pre-cooling heat exchanger and a dilution refrigeration unit. The pulse tube refrigeration unit includes a pulse tube refrigeration part. The throttling refrigeration unit includes a throttling refrigeration part, and the throttling refrigeration part is connected with the adsorption refrigeration unit through the second pre-cooling heat exchangers so as to pre-cool the adsorption refrigeration unit. The adsorption refrigeration unit includes an adsorption refrigeration part, and the adsorption refrigeration part is connected with the dilution refrigeration unit through the third pre-cooling heat exchanger. The dilution refrigeration unit includes a dilution refrigeration part, and the dilution refrigeration part is a refrigeration terminal of the sub-Kelvin temperature zone refrigeration mechanism.

A regenerator for a cryocooler includes a cell, a flow passage, a capillary and supporting elements. A cell wall encloses a cavity with sub-cavities. A connecting passage connects a first sub-cavity to a second sub-cavity. A first cell partition is disposed between the first and second sub-cavities. The flow passage is also disposed between the first and second sub-cavities. During operation of the regenerator, helium in the cavity functions as a heat-storing material, while helium that flows through the flow passage functions as a working gas. The capillary forms a pressure-equalizing opening in the cell wall and connects the helium that functions as the heat-storing material inside the cavity to the helium that functions as the working gas outside the cavity. The supporting elements are inside the first sub-cavity and separate the first cell partition from a second cell partition. The first and second cell partitions enclose the first sub-cavity.