Joule-thomson cryocooler

Abstract

A Joule-Thomson cryocooler includes a pre-cooling cryocooler that includes a pre-cooling stage, a refrigerant circuit that includes a heat exchanger and a refrigerant pipe extending from the heat exchanger and cooled by the pre-cooling stage, and a heat conduction path that is provided separately from the refrigerant pipe and connects the pre-cooling stage to the heat exchanger to enable conductive cooling of the heat exchanger through the pre-cooling stage.

What is claimed is: 
     
         1 . A Joule-Thomson cryocooler comprising:
 a pre-cooling cryocooler that comprises a pre-cooling stage;   a refrigerant circuit that comprises a heat exchanger and a refrigerant pipe extending from the heat exchanger and cooled by the pre-cooling stage; and   a heat conduction path that is provided separately from the refrigerant pipe and connects the pre-cooling stage to the heat exchanger to enable conductive cooling of the heat exchanger through the pre-cooling stage.   
     
     
         2 . The Joule-Thomson cryocooler according to  claim 1 ,
 wherein the pre-cooling cryocooler comprises a cylinder extending from the pre-cooling stage, and   the heat conduction path comprises:
 a first heat conduction member thermally coupled to the pre-cooling stage and extending from the pre-cooling stage to a side opposite to the cylinder, and 
 a second heat conduction member that thermally couples the first heat conduction member to the heat exchanger. 
   
     
     
         3 . The Joule-Thomson cryocooler according to  claim 1 ,
 wherein the pre-cooling cryocooler comprises a first pre-cooling stage and a second pre-cooling stage that is cooled to a lower temperature than the first pre-cooling stage,   the refrigerant circuit comprises a first heat exchanger, a second heat exchanger that further cools a refrigerant cooled by the first heat exchanger, and a third heat exchanger that further cools the refrigerant cooled by the second heat exchanger, and the refrigerant pipe extends from the second heat exchanger via the second pre-cooling stage to the third heat exchanger, and   the heat conduction path connects the second pre-cooling stage to at least one of the second heat exchanger and the third heat exchanger to enable conductive cooling of the at least one of the second heat exchanger and the third heat exchanger through the second pre-cooling stage.   
     
     
         4 . The Joule-Thomson cryocooler according to  claim 3 ,
 wherein the heat conduction path connects the second pre-cooling stage to the second heat exchanger to enable conductive cooling of the second heat exchanger through the second pre-cooling stage.   
     
     
         5 . The Joule-Thomson cryocooler according to  claim 3 ,
 wherein the pre-cooling cryocooler comprises a cylinder that connects the second pre-cooling stage to the first pre-cooling stage, and   the heat conduction path comprises:
 a stage extension component thermally coupled to the pre-cooling stage and extending from the pre-cooling stage to a side opposite to the cylinder, and 
 a heat conduction plate that thermally couples the stage extension component to the at least one of the second heat exchanger and the third heat exchanger. 
   
     
     
         6 . The Joule-Thomson cryocooler according to  claim 5 ,
 wherein the at least one of the second heat exchanger and the third heat exchanger and the stage extension component are disposed on the same side of the heat conduction plate.   
     
     
         7 . The Joule-Thomson cryocooler according to  claim 1 ,
 wherein the heat conduction path comprises a thermal resistance element.   
     
     
         8 . The Joule-Thomson cryocooler according to  claim 2 ,
 wherein the heat conduction path comprises a thermal resistance element between the heat exchanger and the second heat conduction member, and   a thermal conductivity of the thermal resistance element is smaller than a thermal conductivity of the second heat conduction member.   
     
     
         9 . The Joule-Thomson cryocooler according to  claim 3 ,
 wherein the heat conduction path connects the second pre-cooling stage to the third heat exchanger via a thermal resistance element.   
     
     
         10 . The Joule-Thomson cryocooler according to  claim 5 ,
 wherein the heat conduction path comprises a thermal resistance element between the third heat exchanger and the heat conduction plate, and   a thermal conductivity of the thermal resistance element is smaller than a thermal conductivity of the heat conduction plate.