Fast cooldown miniature refrigerators

A microminiature cryogenic refrigerator for cooling superconductor devices and the like comprising at least three plates of material of low like material of low thermal conductivity bonded together in pressure tight contact over an interface area to provide a stiff laminate, said plates having a central region and a peripheral region, an outermost one of said plates being adapted to carry a device to be cooled adjacent its central region, means forming a low temperature chamber at said central region of said laminate, means forming a micron sized supply fluid passage in the interface area between two of said plates connecting an input fluid port to said low temperature chamber, said supply passage comprising a first section for conducting incoming highly compressed gas and a serially connected smaller diameter second capillary section opening into said low temperature chamber, said supply passage being of spiral configuration, and means forming outflow passages in another interface between two of said plates, said outflow passages extending radially from said low temperature chamber to an exit port adjacent the periphery of said refrigerator whereby the cooled gas flowing through said outflow passages is disposed in heat exchange relation with the incoming gas passing through said supply passage to effectively precool the gas passing through said supply passage.