A variable conductance gas switch for intermediate temperature operation of liquid He/liquid N2 cryostats

Abstract A technique for establishing a stable intermediate temperature stage in liquid He/liquid N 2 double vessel cryostats is described. The tertiary cold stage, which can be tuned to any temperature between 10 and 60 K, is ideal for cooling IR sensors for use in astronomy and physics applications. The device is called a Variable Conductance Gas Switch (VCGS). It is essentially a small chamber, located between the cold stage and liquid helium cold-face, whose thermal conductance may be controlled by varying the pressure of helium gas within the chamber. A key feature of this device is the large range of temperature control achieved with a very small (