Cryostat arrangement comprising a neck tube having a supporting structure and an outer tube surrounding the supporting structure to reduce the cryogen consumption

Abstract

A cryostat arrangement (1) with a vacuum tank (2) and a cryogenic tank (3) are provided. The vacuum tank has at least one neck tube, (4) leading to the cryogenic tank, with a supporting structure (4a) and an outer tube (4b) surrounding the supporting structure. The neck tube provides a connection from the cryogenic tank to a region outside the vacuum tank to allow cryogenic fluid to flow from the cryogenic tank into a region outside the vacuum tank or vice versa. The neck tube mechanically suspends the cryogenic tank inside the vacuum tank, and parts of the neck tube form a diffusion barrier between the interior of the cryogenic tank and the interior of the vacuum tank. The neck tube can connect to other components of the cryostat arrangement in a fluid-tight manner. Heat input from the neck tubes into the cryogenic tank can be considerably reduced thereby.

What is claimed is: 
     
         1 . A cryostat arrangement, comprising a vacuum tank and a cryogenic tank, which is arranged inside the vacuum tank,
 wherein the vacuum tank comprises at least one neck tube having a supporting structure surrounded by an outer tube, the neck tube leading to the cryogenic tank, wherein the neck tube connects an internal volume of the cryogenic tank to a region outside the vacuum tank so that cryogenic fluid can flow out of the cryogenic tank into a region outside the vacuum tank or from the region outside the vacuum tank into the cryogenic tank,   wherein parts of the neck tube used to mechanically suspend the cryogenic tank inside the vacuum tank and parts of the neck tube used to construct a diffusion barrier between an interior of the cryogenic tank and an interior of the vacuum tank are arranged to be spatially separated from one another and are produced from materials which are optimized independently of one another, such that the supporting structure supports a weight of the cryogenic tank, and the outer tube is produced from a material through which the cryogenic fluid cannot diffuse, or through which essentially no cryogenic fluid can diffuse, and   wherein the outer tube is configured to connect to other components of the cryostat arrangement in a fluid-tight manner.   
     
     
         2 . The cryostat arrangement according to  claim 1 , wherein the supporting structure is in a form of an inner tube, and wherein the inner tube connects the internal volume of the cryogenic tank to a region outside the vacuum tank so that the cryogenic fluid from the cryogenic tank can flow into a region outside the vacuum tank or from outside the vacuum tank to flow into a region inside the cryogenic tank. 
     
     
         3 . The cryostat arrangement according to  claim 2 , wherein the outer tube is in direct contact with the inner tube. 
     
     
         4 . The cryostat arrangement according to  claim 2 , wherein the outer tube is at a distance from the inner tube, and a gap remains open between the inner tube and the outer tube. 
     
     
         5 . The cryostat arrangement according to  claim 4 , wherein the outer tube and the inner tube are interconnected by a plurality of axially arranged, radially extending thermal bridges. 
     
     
         6 . The cryostat arrangement according to  claim 1 , wherein the supporting structure is produced from plastics material that is fiber reinforced. 
     
     
         7 . The cryostat arrangement according to  claim 1 , wherein the supporting structure made of plastics material comprises a metal extension at each of its two ends. 
     
     
         8 . The cryostat arrangement according to  claim 7 , wherein the metal extensions each have a length of between 20 mm and 100 mm and a cross-sectional area of stress of between 50 mm 2  and 500 mm 2 . 
     
     
         9 . The cryostat arrangement according to  claim 1 , wherein the outer tube is produced from metal. 
     
     
         10 . The cryostat arrangement according to  claim 1 , wherein inside an inner tube of the neck tube and/or between the supporting structure and the outer tube, baffles are installed, which absorb thermal radiation and prevent convection. 
     
     
         11 . The cryostat arrangement according to  claim 11 , wherein the baffles are foldable. 
     
     
         12 . The cryostat arrangement according to  claim 2 , wherein an upper end of the inner tube is closed in a fluid-tight manner in normal operation by a pressure relief valve or a rupture disk, allowing the cryogenic fluid flowing away in normal operation to flow through a gap between the inner tube and the outer tube. 
     
     
         13 . The cryostat arrangement according to  claim 1 , wherein the cryostat contains a Joule-Thomson (JT) cooler, in which the cryogenic fluid is depressurized using a pump located outside the vacuum tank, and the gap between the supporting structure and the outer tube is part of a connecting line between the JT cooler and the pump. 
     
     
         14 . The cryostat arrangement according to  claim 4 , wherein the gap between the inner tube and the outer tube comprises a flow restrictor at an end of the neck tube which is near the cryogenic tank. 
     
     
         15 . The cryostat arrangement according to  claim 1 , wherein the outer tube comprises at least one bellows portion so that the outer tube does not absorb any axial forces. 
     
     
         16 . The cryostat arrangement according to  claim 1 , wherein the neck tube is produced from a material for which:
 σ is a maximum permissible mechanical stress, and σ>100 MPa;   θ is an integral of the thermal conductivity λ over the temperature range ΔT between 300 K and 4 K, and θ<300 W/m; and   wherein a ratio σ/θ>⅓ (MPa·m)/W.   
     
     
         17 . The cryostat arrangement according to  claim 1 , wherein an integral leakage rate out of the cryogenic tank into the vacuum tank is less than 10 −6  mbar·l/s. 
     
     
         18 . The cryostat arrangement according to  claim 2 , wherein the outer tube is in thermal contact with the inner tube. 
     
     
         19 . The cryostat arrangement according to  claim 6 , wherein the fiber-reinforced plastics material is G10. 
     
     
         20 . The cryostat arrangement according to  claim 7 , wherein the metal extension is made of stainless steel. 
     
     
         21 . The cryostat arrangement according to  claim 8 , wherein the outer tube is made of stainless steel.