Cryostat configuration

Abstract

A cryostat configuration for keeping liquid helium comprising an outer jacket ( 3 ) surrounding a helium container ( 1 ) connected at at least two suspension tubes ( 2 ) to the outer jacket ( 3 ), wherein the helium container ( 1 ) also comprises a neck tube ( 5 ) whose upper warm end is connected to the outer jacket ( 3 ) and whose lower cold end is connected to the helium container ( 1 ) and into which a multi-stage cold head ( 6 ) of a cryocooler is installed, wherein the outer jacket ( 3 ), the helium container ( 1 ), the suspension tubes ( 2 ) and the neck tube ( 5 ) delimit an evacuated space ( 7 ), and the helium container ( 1 ) is surrounded by at least one radiation shield ( 4 ) which is connected in a heat-conducting fashion to the suspension tubes ( 2 ) and also to the neck tube ( 5 ) of the helium container ( 1 ) is characterized in that there is a direct connection ( 8 ) between the warm ends of the suspension tubes ( 2 ) and the neck tube ( 5 ) through which helium gas can flow. A cryostat configuration of this type considerably reduces or completely eliminates the heat input via the suspension tubes of an actively cryocooler-cooled NMR magnet system, as a result of which a less powerful cryocooler can be used.

1 . A cryostat configuration for keeping liquid helium, the cryostat configuration comprising: 
 an outer jacket;    a helium container disposed within said outer jacket;    a first suspension tube connected between said helium container and said outer jacket;    a second suspension tube connected between said helium container and said outer jacket;    a neck tube, said neck tube having a warm upper end connected to said outer jacket and a cold lower end connected to said helium container, wherein said outer jacket, said helium container, said first suspension tube, said second suspension tube, and said neck tube delimit an evacuated space;    a multi-stage cryocooler cold head disposed within said neck tube;    a radiation shield surrounding said helium container, said radiation shield being connected in a heat-conducting fashion to said first and second suspension tubes and to said neck tube; and    direct connection means disposed between a warm end of said neck tube and warm ends of said first and said second suspension tubes, said direct connection means structured and dimensioned for helium gas flow therein.    
   
   
       2 . The cryostat configuration of  claim 1 , wherein said cold head of said cryocooler has several stages.  
   
   
       3 . The cryostat configuration of  claim 1 , wherein said cryocooler is a pulse tube cooler.  
   
   
       4 . The cryostat configuration of  claim 1 , wherein helium can be liquefied at a temperature of 4.2K or less at a coldest cold stage of said cryocooler cold head.  
   
   
       5 . The cryostat configuration of  claim 1 , wherein said cold head comprises tubes surrounded with thermal insulation and disposed above a first cold stage.  
   
   
       6 . The cryostat configuration of  claim 5 , wherein said tubes are disposed in a region of further cold stages.  
   
   
       7 . The cryostat configuration of  claim 5 , wherein said thermal insulation and a neck tube wall define a gap or a channel through which gas can flow.  
   
   
       8 . The cryostat configuration of  claim 1 , wherein said neck tube has a thin wall and is made from a material having poor thermal conductivity.  
   
   
       9 . The cryostat configuration of  claim 1 , wherein said neck tube is designed like a bellows and is made from a material having poor thermal conductivity.  
   
   
       10 . The cryostat configuration of  claim 1 , further comprising a heater disposed or in contact with said helium container.  
   
   
       11 . The cryostat configuration of  claim 10 , wherein said heater is an electric heater.  
   
   
       12 . The cryostat configuration of  claim 1 , wherein one or more cold stages of said cold head, which are not a coldest cold stage, are connected to one or more radiation shields in a heat-conducting fashion.  
   
   
       13 . The cryostat configuration of  claim 1 , wherein said radiation shield comprises a container having liquid nitrogen which is connected in a heat-conducting fashion to said cold head of said cryocooler, wherein evaporated nitrogen is at least partially reliquefied by said cold head of said cryocooler.  
   
   
       14 . The cryostat configuration of  claim 13 , further comprising a second heater disposed in or in contact said nitrogen container.  
   
   
       15 . The cryostat configuration of  claim 14 , wherein said second heater is an electric heater.  
   
   
       16 . The cryostat configuration of  claim 1 , further comprising a gas flow control valve disposed in said connection means between said first and said second suspension tubes and said neck tube.  
   
   
       17 . The cryostat configuration of  claim 1 , further comprising a controllable circulating pump disposed in said connection means between said first and said second suspension tubes and said neck tube.  
   
   
       18 . The cryostat configuration of  claim 1 , wherein the cryostat configuration contains a superconducting magnet arrangement.  
   
   
       19 . The cryostat configuration of  claim 18 , wherein the superconducting magnet arrangement is part of an apparatus for magnetic resonance, for magnetic resonance imaging (MRI), or for nuclear magnetic resonance spectroscopy (NMR).