Low-loss cryostat configuration

Abstract

A cryostat configuration ( 10 ), with at least one cryostat ( 11 ), which has at least one first chamber ( 1 ) with supercooled liquid helium having a temperature of less than 4 K and at least one further chamber ( 2 ), which contains liquid helium having a temperature of approximately 4.2 K, a Joule-Thomson valve ( 3 ) being disposed in the first chamber, wherein the first chamber is separated from the further chamber by a thermally insulating barrier ( 4 ), wherein helium from the first or the further chamber expands through the Joule-Thomson valve into a pump-off pipe ( 13 ), which is in thermal contact with the helium of the first chamber and supercools the latter, and wherein the pump-off pipe is directly or indirectly in thermal contact with the further chamber during its further progression and is then connected to the inlet of a pump ( 14 ), is characterized in that the outlet of the pump and/or an outlet for evaporating helium of at least one of the cryostats is fluidically connected to the further chamber through a cryogen pipe ( 15 ), and that the cryogen pipe has a branch-off device ( 16 ), which returns a partial current of the helium located in the cryogen pipe into the further chamber. In this way, the helium consumption and therefore the operating costs are reduced while the pressure in the first chamber remains constant.

1 . A cryostat configuration comprising:
 at least one cryostat, said cryostat having at least one first chamber disposed, structured and dimensioned to keep supercooled liquid helium at a temperature of less than 4 K, said cryostat also having at least one further chamber disposed, structured and dimensioned to keep helium under atmospheric pressure at a temperature of approximately 4.2 K, said cryostat having an outlet for evaporating helium;   a Joule-Thomson valve disposed in said first chamber;   a thermally insulating barrier disposed to separate said first chamber from said further chamber;   a pump-off pipe in thermal contact with helium of said first chamber, a further progression of said pump-off pipe being in direct or indirect thermal contact with said further chamber;   a pump, said pump having an inlet connected to said pump-off pipe to urge helium from said first or said further chamber to expand through said Joule-Thomson valve into said pump-off pipe, thereby supercooling helium in said first chamber, said pump also having an outlet;   a cryogen pipe in fluid connection between said further chamber and said outlet of said pump and/or said evaporating helium outlet of said cryostat, said cryogen pipe having a branch-off device, which returns a partial current of helium located in said cryogen pipe into said further chamber.   
     
     
         2 . The cryostat configuration of  claim 1 , wherein said first chamber and said further chamber are hydrostatically connected to each other. 
     
     
         3 . The cryostat configuration of  claim 1 , wherein said further chamber is disposed above said first chamber. 
     
     
         4 . The cryostat configuration of  claim 1 , further comprising a pressure regulating device for keeping a constant pressure in said further chamber. 
     
     
         5 . The cryostat configuration of  claim 4 , further comprising a heating device disposed in said further chamber. 
     
     
         6 . The cryostat configuration of  claim 4 , wherein said pressure regulating device adjusts a pressure in said further chamber to a settable target pressure that is greater than or equal to an ambient pressure of the cryostat configuration. 
     
     
         7 . The cryostat configuration of  claim 5 , wherein said pressure regulating device adjusts a pressure in said further chamber to a settable target pressure that is greater than or equal to an ambient pressure of the cryostat configuration. 
     
     
         8 . The cryostat configuration of  claim 4 , wherein said pressure regulating device sets a pressure in said further chamber to a defined positive pressure above atmospheric pressure. 
     
     
         9 . The cryostat configuration of  claim 5 , wherein said pressure regulating device sets a pressure in said further chamber to a defined positive pressure above atmospheric pressure. 
     
     
         10 . The cryostat configuration of  claim 1 , wherein said cryogen pipe has at least one relief valve and/or at least one bursting disk. 
     
     
         11 . The cryostat configuration of  claim 1 , wherein said cryogen pipe contains a buffer vessel for provision of an additional volume for helium located in said cryogen pipe. 
     
     
         12 . The cryostat configuration of  claim 1 , wherein said cryogen pipe has at least one filtering device for separating off impurities in flowing helium. 
     
     
         13 . The cryostat configuration of  claim 1 , wherein said partial flow returned into said further chamber comprises between 20% and 80% of a total helium flow conveyed through said pump. 
     
     
         14 . The cryostat configuration of  claim 13 , wherein said partial flow returned into said further chamber comprises between 25% and 60% of a total helium flow conveyed through said pump. 
     
     
         15 . The cryostat configuration of  claim 1 , wherein helium is input into said cryogen pipe from at least one further, physically separate cryostat. 
     
     
         16 . The cryostat configuration of  claim 1 , further comprising a superconducting magnet coil disposed in said first chamber. 
     
     
         17 . The cryostat configuration of  claim 16 , wherein the cryostat configuration is part of NMR, MRI, or FTMS equipment. 
     
     
         18 . The cryostat configuration of  claim 17 , wherein the equipment comprises an ultrahigh-resolution high-field NMR spectrometer with a proton resonance frequency ≧800 MHz.