Device for loss-free cryogen cooling of a cryostat configuration

Abstract

A cooling device ( 7 ) for re-liquefying cryogenic gases, comprising an outer jacket ( 8 ) which delimits a vacuum chamber ( 9 ), and a cryocooler cold head ( 10 ) installed therein, which has at least two cold stages ( 11, 12 ) and is at least partially surrounded by a radiation shield ( 13 ) is characterized in that at least two cold stages ( 11, 12 ) of the cold head ( 10 ) are separately individually connected in a heat-conducting manner to a heat-transferring device ( 14 a, 14 b ) which can be inserted into the neck or suspension tubes ( 3 a, 3 b ) of a cryostat ( 1 ) for keeping at least two different cryogenic liquids ( 18 a, 18 b ). The cooling device can be easily retrofitted into existing cryostat configurations, in particular, those containing superconducting magnets and without (or with minimum) adjustment to permit operation with no or little cryogen loss, even if several cryogens are used.

1 . A cooling device for re-liquefying cryogenic gases emanating from a cryostat, the cryostat keeping at least two different cryogenic liquids, the cryostat having neck and suspension tubes, the cooling device comprising: 
 a first cryocooler cold head stage;    a second cryocooler cold head stage;    a radiation shield surrounding at least portions of said first and said second stages;    an outer jacket delimiting a vacuum chamber, said jacket surrounding said radiation shield and said first and said second stages;    a first heat transferring device in heat-conducting connection with said first cold head stage; and    a second heat transferring device in heat-conducting connection with said second cold head stage, said first and said second heat transferring devices structured and dimensioned for insertion into the neck or the suspension tubes of the cryostat.    
   
   
       2 . The cooling device of  claim 1 , wherein at least one of said first and said second heat-transferring devices has a cavity disposed in heat-conducting contact with said first or said second cold stage, said cavity connected to an open line or conduit feeding into a liquid tank of the cryostat, wherein cryogen is evaporated from the liquid tank and enters into said cavity where it is liquefied to subsequently flow back through said open line or conduit into the liquid tank.  
   
   
       3 . The cooling device of  claim 1 , wherein at least one of said first and said second heat-transferring devices has a metallic connection with excellent heat conducting properties at the end of which cryogen evaporated from a liquid tank of the cryostat is liquefied and subsequently returned into a liquid bath of the liquid tank.  
   
   
       4 . The cooling device of  claim 1 , wherein said cryocooler is a pulse tube cooler.  
   
   
       5 . The cooling device of  claim 1 , wherein said cryocooler is a Gifford-McMahon cooler.  
   
   
       6 . The cooling device of  claim 1 , further comprising at least one connecting line, which is open at both ends, to connect said cold head of said cryocooler to at least one neck or suspension tube, in which no heat-transferring device is inserted, of a liquid tank containing a cryogen having a lowest boiling temperature, wherein said line is in thermal contact with said first and said second cold stages of said cold head.  
   
   
       7 . The cooling device of  claim 6 , wherein said line is in thermal contact with a regenerator tube disposed above a coldest cold stage and said line terminates in said cavity or is guided along a metallic connection into the liquid tank after thermal contact with said coldest cold stage.  
   
   
       8 . The cooling device of  claim 6 , further comprising a valve and/or a pump inserted into said connecting line between the neck or suspension tube and said cold head.  
   
   
       9 . The cooling device of  claim 1 , wherein helium can be liquefied at a temperature of 4.2 K or less at a coldest stage of said cryocooler.  
   
   
       10 . The cooling device of  claim 1 , wherein liquid nitrogen can be generated at 77K or less at a cold stage of said cold head of said cryocooler.  
   
   
       11 . The cooling device of  claim 1 , wherein a cold stage of said cold head of said cryocooler, which is not a coldest cold stage, is connected in a heat-conducting manner to said radiation shield which at least partially surrounds said cold head.  
   
   
       12 . The cooling device of  claim 1 , wherein at least one of said first and said second heat-transferring device is at least partially disposed within said outer jacket.  
   
   
       13 . The cooling device of  claim 2 , wherein at least one of said first and said second the heat-transferring device is at least partially surrounded by a first tube in a region outside of said outer jacket.  
   
   
       14 . The cooling device of  claim 13 , wherein said first tube is open at one end, that end being connected to a vacuum chamber of said outer jacket while an other end is connected in a gas-tight manner to one of said first and said second heat-transferring devices.  
   
   
       15 . The cooling device of  claim 13 , wherein said first tube is connected at both ends in a gas-tight manner to one of said first and said second heat-transferring devices and is provided with a separate connection for evacuation.  
   
   
       16 . The cooling device of  claim 13 , wherein said conduit or a metallic connection of said first or said second heat-transferring device is at least partially surrounded by a second tube which is connected in a heat-conducting manner to said radiation shield, wherein said second tube is disposed within said first tube.  
   
   
       17 . The cooling device of  claim 16 , wherein said first and said second tubes are flexible or are designed as bellows.  
   
   
       18 . The cooling device of  claim 2 , wherein said conduit or a metallic connection comprises a flexible section, a bellows, or wires which are plaited into strands.  
   
   
       19 . The cooling device of  claim 16 , wherein in at least one of said first and said second heat-transferring devices and a least one of said first and said second tubes can be connected and disconnected at at least one point using a gas-tight coupling.  
   
   
       20 . The cooling device of  claim 1 , wherein the cooling device can be mounted in a gas-tight manner to the cryostat for keeping cryogenic liquids.  
   
   
       21 . The cooling device of  claim 1 , wherein the cooling device can be mounted outside of the cryostat.  
   
   
       22 . The cooling device of  claim 21 , further comprising a soft connecting element which does not transmit vibrations and which is sealingly disposed between the cooling device and the cryostat.  
   
   
       23 . The cooling device of  claim 1 , further comprising electric heaters mounted to at least one of said first and said second cold stages of said cryocooler.  
   
   
       24 . A cryostat configuration characterized by the cooling device of  claim 1 .  
   
   
       25 . The cryostat configuration of  claim 24 , further comprising a superconducting magnet arrangement, wherein said cooling device serves to cool said superconducting magnet arrangement.  
   
   
       26 . The cryostat configuration of  claim 25 , wherein said superconducting magnet arrangement is part of an apparatus for nuclear magnetic resonance, magnetic resonance imaging (MRI), or magnetic resonance spectroscopy (nuclear magnetic resonance NMR).  
   
   
       27 . The cryostat configuration of  claim 24 , further comprising an electric heater inserted into a cryogenic liquid tank via the suspension or neck tubes thereof.