Patent ID: 8418480

Claim:
A cryogenic liquid cooling system, comprising: a dewar configured to store unpressurized cryogenic liquid, said dewar comprising at least one vent portal for venting the cryogenic liquid in the dewar to the ambient atmosphere outside the dewar; a positive displacement pump configured to pump the unpressurized cryogenic liquid from the dewar through a transfer line without interruption when the positive displacement pump is submerged within the cryogenic liquid; and a drive assembly mechanically coupled to the positive displacement pump, wherein the drive assembly is configured to provide a reciprocating motion to the positive displacement pump, and wherein the drive assembly is configured to attach to the dewar, whereby the drive assembly is disposed outside the dewar during operation of the positive displacement pump; a heat exchanger comprising an annular cavity for receiving the cryogenic liquid; a sample stage of a scientific instrument coupled to the heat exchanger by being mounted on a mounting surface in a central cavity of the heat exchanger, said heat exchanger configured to: receive the cryogenic liquid pumped through the transfer line into the annular cavity; transfer heat away from the mounting surface and thus from the sample stage of the scientific instrument, wherein heat is transferred away from the mounting surface and thus from the sample stage of the scientific instrument by vaporization of the cryogenic liquid within the annular cavity in the heat exchanger; wherein the positive displacement pump operates to supply a continuous flow of cryogen to the heat exchanger that is sufficient to compensate for a maximum heat load applied to the heat exchanger by the sample stage and return unvaporized cryogenic liquid and vapor evolved from the cryogenic liquid to the dewar, wherein the at least one portal remains open to the atmosphere to allow excess cryogen vapor to vent to the outside atmosphere during operation of the pump; wherein the heat exchanger includes an exhaust tube configured such that a level of cryogenic liquid in the heat exchanger during operation corresponds an elevation of the exhaust tube.