Undercooled horizontal cryostat configuration

Abstract

A cryostat configuration has a magnet coil system ( 2 ) disposed in a helium tank ( 1 ), and a horizontal room temperature bore ( 3 ) which provides access to a volume under investigation in the center of the magnet coil system ( 2 ). The helium tank ( 1 ) contains undercooled liquid helium at a temperature of less than 3.5 K, in particular of approximately 2 K, and the cryostat configuration has at least one vertical tower structure ( 4 ) on its upper side for filling in and evaporating helium. The tower structure ( 4 ) contains a container ( 5 ) with liquid helium of 4.2 K which is separated from the helium tank ( 1 ) by a thermal barrier ( 7 ), and the helium tank ( 1 ) contains an undercooling unit ( 9 ). This yields a compact cryostat configuration which achieves continuous, stable long-term operation with an undercooled high-field magnet coil.

1 . A cryostat configuration for a magnet coil system, the cryostat configuration comprising:
 a helium tank in which the magnet coil system is disposed, said helium tank having a horizontal room temperature bore providing access to a volume under investigation in a center of the magnet system, said helium tank structured to contain undercooled liquid helium at a temperature of less than 3.5 K or of approximately 2 K;   a vertical tower structure disposed on an upper side of the cryostat configuration for filling-in and for evaporation of helium;   a container structured for holding liquid helium at 4.2 K, said container disposed in said vertical tower structure;   a thermal barrier disposed to thermally separate said container from said helium tank;   an undercooling unit disposed in said helium tank; and   a radiation shield, said radiation shield having a horizontal component surrounding said helium tank and said room temperature bore, said horizontal component extending substantially cylindrically about a horizontal axis, said radiation shield also having a vertical component cooperating with an upper side of said horizontal component and extending in an upward direction to surround and enclose said container, said vertical component extending substantially cylindrically about a vertical axis.   
     
     
         2 . The cryostat configuration of  claim 1 , further comprising at least two radiation shields disposed outside of said helium tank. 
     
     
         3 . The cryostat configuration of  claim 2 , wherein said tower structure has at least one additional tower on an upper side thereof in which helium evaporating from the cryostat configuration discharges enthalpy to said radiation shields. 
     
     
         4 . The cryostat configuration of  claim 3 , further comprising at least two or three annularly disposed additional towers and throttles with predetermined flow cross-section for uniform distribution of pumped helium to said additional towers. 
     
     
         5 . The cryostat configuration of  claim 4 , further comprising flow detectors to measure a flow rate of evaporating helium through said additional towers, and a flow device to automatically control a flow rate of evaporating helium through said additional towers. 
     
     
         6 . The cryostat configuration of  claim 3 , further comprising a hollow tube annular heat exchanger disposed in said additional tower, through which helium evaporating and/or being pumped out of the cryostat configuration is guided to an outside, wherein said radiation shields are thermally coupled to an outer side of said heat exchanger. 
     
     
         7 . The cryostat configuration of  claim 2 , further comprising a refrigerator or a pulse tube cooler that projects into said container to re-liquefy helium. 
     
     
         8 . The cryostat configuration of  claim 7 , wherein said refrigerator has two stages and cools at least one of said radiation shields. 
     
     
         9 . The cryostat configuration of  claim 2 , wherein liquid helium pumped by said undercooling unit cools at least one of said radiation shields. 
     
     
         10 . The cryostat configuration of  claim 1 , wherein helium is removed from said helium tank or said container via said undercooling unit. 
     
     
         11 . The cryostat configuration of  claim 7 , wherein said container is connected to an external reservoir with gaseous helium, said reservoir being slightly overpressurized relative to atmospheric pressure. 
     
     
         12 . The cryostat configuration of  claim 11 , wherein liquid helium pumped by said undercooling unit is pumped into said reservoir. 
     
     
         13 . The cryostat configuration of  claim 12 , wherein said external reservoir is connected to said refrigerator. 
     
     
         14 . The cryostat configuration of  claim 13 , wherein said external reservoir is exclusively connected to said refrigerator. 
     
     
         15 . The cryostat configuration of  claim 1 , further comprising a heating element disposed in said container. 
     
     
         16 . The cryostat configuration of  claim 1 , wherein said helium tank and said container define a separated tank, wherein said helium tank is disposed below said container. 
     
     
         17 . The cryostat configuration of  claim 1 , wherein said thermal barrier separating said container from said helium tank consists essentially of a material having poor heat conducting properties. 
     
     
         18 . The cryostat configuration of  claim 1 , wherein said thermal barrier comprises of at least two plates which are substantially separated by a vacuum, said vacuum being part of a uniform vacuum within the cryostat configuration. 
     
     
         19 . The cryostat configuration of  claim 1 , further comprising a pressure control means disposed in said thermal barrier to open an increased pressure compensation cross-section in said thermal barrier when a certain pressure difference between said helium tank and said container has been exceeded and/or further comprising at least one rupture disc disposed in at least one wall of said container which does not border the helium tank, said disc opening a large cross-section to an outside of the cryostat configuration when a maximum pressure in said container has been exceeded. 
     
     
         20 . The cryostat configuration of  claim 1 , wherein a limited flow cross-section, a pressure compensation gap, or an annular gap is defined between said helium tank and said container, through which liquid helium can flow from said container into said helium tank. 
     
     
         21 . The cryostat configuration of  claim 19 , wherein said pressure control valve comprises a stopper or a conical stopper having heat exchanging surfaces directed into said container and said helium tank, wherein said stopper is inserted into a seat in said thermal barrier, said seat having a shape congruent to said stopper. 
     
     
         22 . The cryostat configuration of  claim 1 , wherein electric feed lines required for charging a superconducting magnet coil of the magnet coil system are initially guided through said container before entering said helium tank, and further comprising devices for short-circuit operation of the magnet coil, wherein said electric feed lines to the magnet coil are removed after short-circuiting. 
     
     
         23 . The cryostat configuration of  claim 1 , wherein a center of the magnet coil system, in a radial direction, does not coincide with a center of said container surrounding the magnet coil system. 
     
     
         24 . The cryostat configuration of  claim 1 , wherein a center of the magnet coil system and a center of said container are disposed in different planes, perpendicular to an axis of the room temperature bore.