Cryogenic cooling device and method

Abstract

Cryogenic cooling method and device comprising a main cryogenic cooler comprising a cold head positioned in a first chamber selectively placed under vacuum, a reservoir of working fluid placed in a second chamber selectively placed under vacuum, a member to be cooled being placed in the reservoir in heat exchange with the working fluid, the cold head of the main cryogenic cooler being thermally connected to a heat exchanger which is itself fluidically connected to the reservoir via pipes forming a first circulation loop for the working fluid, the pipes passing from the first to the second chamber, characterized in that the volumes selectively under vacuum of the first and second chambers are independent and in that the device comprises a secondary cryogenic cooler comprising a cold head placed in a third chamber selectively placed under vacuum, the cold head of the secondary cryogenic cooler being thermally connected to a heat exchanger which is itself fluidically connected to the reservoir via pipes forming a second circulation loop for the working fluid, and in that the volume selectively under vacuum of the third chamber is independent of the volumes selectively under vacuum of the first and second chambers.

1 - 13 . (canceled) 
     
     
         14 . A cryogenic cooling device comprising a main cryocooler with a cold head arranged in a first chamber placed under vacuum, a reservoir of working fluid arranged in a second chamber placed under vacuum, a member that is to be cooled being arranged in the reservoir in a heat exchange relationship with the working fluid, and a secondary cryocooler comprising a cold head arranged in a third chamber placed under vacuum, wherein:
 the cold head of the main cryocooler is thermally connected to a heat exchanger, itself fluidically connected to the reservoir via pipes forming a first circulation loop for the working fluid, the pipes passing from the first to the second chamber;   the volumes under vacuum of the first and second chambers are independent which means to say that the vacuums in the first and second chambers are independent;   the cold head of the secondary cryocooler is thermally connected to a heat exchanger, itself fluidically connected to the reservoir via pipes forming a second circulation loop for the working fluid; and   the volume under vacuum of the third chamber is independent of the volumes under vacuum of the first and second chambers which means to say that the vacuums of the first, second and third chambers are independent.   
     
     
         15 . The device of  claim 14 , wherein at least one of the first and third chambers is sealed off by at least one selectively removable cap. 
     
     
         16 . The device of  claim 15 , wherein at least one selectively removable cap is arranged in the lower part of the chamber such that it is adjacent to the cold head. 
     
     
         17 . The device of  claim 15 , wherein at least one cap is mounted in a sealed fashion on the body of the chamber via fixing screws. 
     
     
         18 . The device of  claim 14 , further comprising, around the pipes passing from the first to the second chamber, vacuum barriers which separate the volumes under vacuum of the first and second chambers, the vacuum barriers being arranged in at least one tubular portion that connects the first and second chambers. 
     
     
         19 . The device of  claim 14 , further comprising, around the pipes passing from the third to the second chamber, vacuum barriers which separate the volumes under vacuum of the third and second chambers, the vacuum barriers being arranged in at least one tubular portion that connects the third and second chambers. 
     
     
         20 . The device of  claim 14 , wherein the cold head of the cryocooler(s) is associated with a heat exchanger that acts as a condenser for the working fluid. 
     
     
         21 . The device of  claim 14 , wherein the cold head of the main cryocooler is connected to the reservoir via two pipes the upstream ends of which are connected to a hermetic volume arranged under the cold head of the main cryocooler, the downstream ends of the pipes being connected to an upper end of the reservoir via a vertical or substantially vertical portion. 
     
     
         22 . The device of  claim 14 , wherein the cold head of the secondary cryocooler is connected to the reservoir via two pipes the upstream ends of which are connected to a hermetic volume arranged under the cold head of the secondary cryocooler and the downstream ends of which are connected to an upper end of the reservoir via a vertical or substantially vertical portion. 
     
     
         23 . A method for cooling a member to a low temperature using the cryogenic cooling device of  claim 14 , wherein the main cryocooler is used to cool the member, the first chamber and the second chamber are placed under vacuum and the secondary cryocooler is selectively switched off or on while the main cryocooler is in operation. 
     
     
         24 . The method of  claim 23 , wherein the main cryocooler is switched off, and at the same time or before the main cryocooler is switched off, the secondary cryocooler is started in order to cool the member, the third chamber being placed under vacuum or kept under vacuum. 
     
     
         25 . The method of  claim 23 , wherein when a cryocooler is switched off, the cold head of the cryocooler switched off is heated up to an ambient temperature using at least one of the following steps:
 spontaneous natural heating;   by commanded active heating;   by forced circulation of gas at ambient temperature into the chamber of the cryocooler or around the exchangers via a coiled tube or any other device; and   by bringing the volume of the cryocooler chamber to atmospheric pressure.   
     
     
         26 . The method of  claim 23 , further comprising a step of repairing or maintaining one of the two cryocoolers while the other cryocooler is in operation and is cooling the member, the method comprising:
 shutting down the cryocooler intended to undergo repair or maintenance or keeping it in the switched off state;   keeping the cryocooler intended to undergo repair or maintenance at ambient temperature or bringing it to ambient temperature;   opening the chamber containing the cryocooler intended to undergo repair or maintenance;   dismantling the cryocooler intended to undergo repair or maintenance so that it can be replaced or repaired without connected the hermetic volume to the atmosphere; and   maintaining the vacuum within the chamber of the other cryocooler that is in operation and in the second chamber.