Patent ID: 6854276

Claim:
A method for achieving and maintaining cryogenic cooling for a cryogenic cooling system having a cryogen containment vessel that stores cryogen in a liquid state and a gaseous state, wherein the liquid state includes a subcooled region and a thermal gradient layer (TGL) boundary region adjacent the gaseous region and having at least one superconductor, the method comprising the steps of: maintaining a pressurized cryogen region within the cryogen containment vessel; maintaining the temperature of the subcooled region of the liquid cryogen at or below its boiling temperature using sub-cooling means; and maintaining an optimum thickness of the TGL, wherein the optimum thickness of such TGL in the case of a stagnat liquid cryogen is expressed by the equation k×S×(ΔT)/Q, wherein “S” is the surface area of the TGL, and wherein “ΔT” is the temperature difference across the TGL region, and wherein “k” is the thermal conductivity of the cryogen in the TGL, and wherein “Q” is the heat input to the TGL through the boundary surface between the TGL and the gaseous regions; and maintaining a physical barrier between the TGL and subcooled liquid cryogen regions, wherein such barrier is thermally coupled to a cryocooling means, wherein the thermal conductive characteristics of such barrier allows the heat input “Q” to the TGL to be transferred to the subcooled region and/or the coupled cryocooling means.