Cryogenic cooling apparatus

Abstract

The invention provides a controlled connection, or heat switch, between a source of cryogenic cooling and an item which is to be cooled, using control valve means which is not itself subjected to the cryogenic temperatures involved. In one aspect, the invention provides cooling means, comprising a source of flow of a fluid, a supply line for supplying fluid from said source to a first heat exchanger, where it is cooled by a source of cryogenic cooling, and thereafter to a second heat exchanger where it is in heat-exchanging relationship with an item to be cooled by the cryogenic cooling source, and a return line for return flow of the fluid from the second heat exchanger to the fluid flow source, the return line and the supply line between the fluid flow source and the first heat exchanger being in heat exchange relationship with one another in a third heat exchanger, wherein between the fluid flow source and the third heat exchanger there is included in the supply line or the return line a control valve whereby the flow of fluid through the supply line and from the first to the second heat exchanger can be controlled. One embodiment is constituted by a multi-stage cryogenic cooling apparatus having a closed-loop Joule-Thomson expansion the compressor via a low-pressure return line), and a Joule-Thomson stage heat exchanger in which the high-pressure line and the low-pressure return line are in heat-exchanging relationship, and the pre-cooler stage being arranged to pre-cool gas in the high-pressure line before it enters the Joule-Thomson stage heat exchanger, wherein the high-pressure gas line of the Joule-Thomson stage is provided, upstream of its interaction with the pre-cooler stage, with a branch leading through a bypass valve.

Dependencies are inferred from the claim text.