Reliquifier

Abstract

A reliquifier using a cryocooler in which an insulated sleeve surrounds a portion of the cold head, a first stage cooling station, and a second stage cooling station, including a condenser. Gas is conveyed from a cryostat to the insulated sleeve, where it is liquefied as it passes over the cold head. An end of the insulated sleeve is connected to a liquid transfer tube for conveying condensed fluid back to the cryostat.

1 . A reliquifier for recondensing boiled off cryogen from a cryostat, comprising:
 a cryocooler cold head comprising a hot end and a cold end, at least one cooling station at the cold end, and a condenser thermally coupled to the cooling station at the cold end;   a vacuum insulated sleeve with an upper end and a liquid end, surrounding the cold end of the cold head of the cryocooler, the at least one cooling station and the condenser; and   a gas trapping tube between the upper end of the sleeve and a gas outlet of the cryostat; and   a liquid transfer tube with a first end connected to the liquid end of the vacuum insulated sleeve and a second end in fluid communication with the cryostat,   such that gas from the cryostat is conducted through the gas trapping tube from the cryostat to the upper end of the sleeve, precooled by passage around the cryocooler cold head, recondenses into fluid on the condenser, and the recondensed fluid passes from the condenser within the insulated sleeve through the liquid transfer tube back into the cryostat.   
     
     
         2 . The reliquifier of  claim 1 , wherein a lower portion of the vacuum insulated sleeve is further surrounded by a radiation shield. 
     
     
         3 . The reliquifier of  claim 1 , further comprising a heat transfer ring surrounding the vacuum insulated sleeve adjacent to the cooling station. 
     
     
         4 . The reliquifier of  claim 3 , wherein the cryocooler is a multi-stage cooler having at least a first stage cooling station and a second stage cooling station, and the cooling station adjacent the heat transfer ring is a first stage cooling station. 
     
     
         5 . The reliquifier of  claim 1 , wherein the cryocooler is multi-stage and the condenser is coupled to a lowest stage cooling station. 
     
     
         6 . The reliquifier of  claim 5 , wherein the cryocooler has a first stage cooling station and a second stage cooling station, the lowest stage cooling station being the second cooling station. 
     
     
         7 . The reliquifier of  claim 6 , wherein the vacuum insulated sleeve is comprised of a first portion surrounding the first stage cooling station and a second portion surrounding the second stage cooling station, the first portion and the second portion of the vacuum insulated sleeve being separated by a heat transfer ring. 
     
     
         8 . The reliquifier of  claim 7 , wherein cooling capacity of the first stage cooling station is transferred to the heat transfer ring through a small gap. 
     
     
         9 . The reliquifier of  claim 7 , wherein cooling capacity of the first stage cooling station is transferred to the heat transfer ring through contact between the heat transfer ring and the first stage cooling station. 
     
     
         10 . The reliquifier of  claim 1 , wherein the vacuum insulated sleeve is surrounded by a vacuum housing. 
     
     
         11 . The reliquifier of  claim 10 , wherein a vacuum space is defined between the vacuum insulated sleeve and the vacuum housing. 
     
     
         12 . The reliquifier of  claim 1 , wherein the liquid transfer tube has at least one bend between the first end connected to the liquid end of the vacuum insulated sleeve and the second end in fluid communication with the cryostat. 
     
     
         13 . The reliquifier of  claim 1 , wherein the liquid transfer tube is straight between the first end connected to the liquid end of the vacuum insulated sleeve and the second end in fluid communication with the cryostat. 
     
     
         14 . The reliquifier of  claim 1 , further comprising an external gas supply coupled to the upper end of the sleeve, such than gas from the external gas supply is liquefied by the reliquifier.