An abstract for a quench valve of a cryostat, in particular for use in a magnetic resonance imaging system, is attachable to the quench valve so as to raise the cracking pressure of the quench valve without changing the operability of the quench valve. Such an accessory device is usable to enable the cryostat, containing a cryogen, to be safely transported by air transportation.

A method is provided for precooling a cryostat having a hollow cold head turret into which a neck tube protrudes and connects an object to be cooled to the exterior of the cryostat, wherein a cold head having a cold head stage for cooling a cryogenic working medium may be introduced into the neck tube. During a condensation operation the cryogenic working medium flows through a heat pipe into an evaporator chamber which is thermally conductively connected to the object to be cooled. During a precooling phase a precisely fitting, thermally conductive short circuit block is inserted through the neck tube into the heat pipe to provide thermal conduction between the object to be cooled and a cooling device. The short circuit block is removed from the heat pipe after the target temperature is reached, and heat is subsequently transmitted through the heat pipe during a condensation operation.

The present invention provides a two stage cryogen cooling system for particular use in cooling a cryogen employed in a superconducting power transmission cable, the cooling system employing a sub-cooler pump such as a venturi pump to effect both cooling stages, the first cooling stage being the cooling of the liquid cryogen flowing through an inner lumen of a cryostat of the cooling system and the second stage being the generation of a supply of gaseous cryogen for supply to a second lumen of the cryostat surrounding the inner lumen.

There is provided a cryogenic link and a method of installing a cryogenic link. The cryogenic link comprises: a core and a cryostat. The cryostat comprises a flexible sleeve around the core and is configured to maintain a temperature of the core at a cryogenic temperature. The cryostat further comprises spacing means configured to maintain a spacing between the core and the flexible sleeve during expansion and contraction of the core. The flexible sleeve is suitable for fixing to an external structure at a plurality of fixed points, where each of the plurality of fixed points is separated by a distance, and a length of the cryogenic link between at least one pair of fixed points is greater than the distance between that pair of fixed points.