Refrigeration of superconducting magnet systems

A liquefier for supplying cryogenic fluid to refrigerate at least one load, said liquefier comprising liquefier parts, including:

• a compressor, refrigerator, refrigerator, and a condenser element downstream therefrom, operatively interconnected and defining a closed loop flow path for a first supply of fluid, and wherein said condenser element is configured for heat exchange with gas outside said flow path therethrough;
• and
• a dewar defining a volume for storage of a cryogenic liquid including ullage thereabove, said cryogenic liquid produced from a second supply of fluid isolated from said first supply of fluid for refrigeration of at least one load;
• wherein said dewar comprises:
• an outer vessel;
• an inner vessel defining said volume suitable for storage of a liquid cryogen including ullage thereabove, said volume further including a separately defined cold vapor storage chamber generally positioned therein, wherein said cold vapor storage chamber is positioned below said ullage space;
• and
• a cold vapor line extending from said ullage to said cold vapor storage chamber;
• whereby vapor may be conveyed between said ullage and said chamber, and stored in said chamber at cryogenic temperatures;
• and
• wherein said condenser element of said evaporation component is positioned in said dewar to liquefy said second fluid in the dewar to refrigerate a load.

A liquefier for supplying cryogenic fluid to refrigerate at least one load, said liquefier comprising liquefier parts, including:

• a compressor, refrigerator, refrigerator, and a condenser element downstream therefrom, operatively interconnected and defining a closed loop flow path for a first supply of fluid, and wherein said condenser element is configured for heat exchange with gas outside said flow path therethrough;
• and
• a dewar defining a volume for storage of a cryogenic liquid including ullage thereabove, said cryogenic liquid produced from a second supply of fluid isolated from said first supply of fluid for refrigeration of at least one load;
• and
• wherein:
• said condenser element of said evaporation component is positioned in said dewar to liquefy said second fluid in the dewar to refrigerate a load;
• said dewar further includes a load comprising at least one superconducting magnet disposed therein to receive cryogenic fluid and having a pair of magnet current leads permanently connected to said magnet to convey electricity between a source of electricity and said magnet;
• at least one of said magnet current leads includes two sets of refrigerant passages, a first set of passages to receive and convey refrigerant vapor or cold gas from a first source of refrigerant, and a second set of passages to receive and convey refrigerant vapor from a second source of refrigerant;
• and
• said at least one lead may be cooled by refrigerant flowing through either said first or second set of passages.

A method for low-cost refrigeration of intermittent pulsed cryogenic loads comprising the steps of:

• providing a helium liquefier, wherein said liquefier:
• comprises liquefier parts operatively interconnected, including a condenser element defining a closed loop flow path for a first supply of helium, and a dewar defining a volume including ullage for a second supply of helium isolated from said first supply of helium, wherein said condenser element is disposed in said ullage;
• and
• wherein at least one pulsed cryogenic load is further disposed in said dewar volume;
• variably operating said liquefier in response to the need for refrigeration of at least one pulsed cryogenic load over said defined duty cycle, and delivering corresponding quantities of refrigeration in said closed loop flow path to at least said condenser element;
• condensing helium in said dewar volume at rates related to the delivered refrigeration, wherein said step of condensing is:
• performed at a maximum rate less than the peak refrigeration requirements of said pulsed cryogenic load during said defined duty cycle;
• and
• variable up to a maximum rate satisfying steady-state refrigeration requirements of said pulsed cryogenic load, plus an additional amount which accumulates over time a buffer volume of liquid helium in said dewar substantially satisfying peak refrigeration requirements of said pulsed cryogenic load during at least one pulse thereof in real time;
• and
• refrigerating said pulsed cryogenic load in said dewar during steady-state operation and pulsing thereof.