CRYOSTAT HAVING HEAT EXCHANGING MEANS IN A VENT TUBE

摘要

A cryostat is disclosed which includes a liquid helium chamber for cooling an object such as a superconducting solenoid to cryogenic temperatures. A vent tube is connected in gas communication with the liquid helium chamber and extends outwardly therefrom for venting vaporized helium. An elongated plug partially closes off the vent tube and defines an annular gas passageway in the space between the plug and the inside wall of the vent through which the evolved gaseous helium is vented for cooling the inside wall of the vent tube. The plug includes a liquid nitrogen chamber and thermal insulation is interposed in the plug between the liquid nitrogen and liquid helium chambers to provide a thermal barrier therebetween. The use of liquid nitrogen in the plug improves the thermal isolation of the liquid helium chamber from the surrounds and reduces the liquid helium consumption.