Experimental Study on Thermal Contact Conductance at Liquid Helium Temperature

Abstract

This chapter employs two methods to estimate this thermal contact conductance at liquid helium temperature–an empirical equation, and the Wiedemann-Franz law. When cooling an object in a cryogen-free, cryocooled system at liquid helium temperature, it is important to quantitatively estimate the thermal resistance that occurs at the contact surface between the cooling stage and the object. It compares the estimated conductance with that measured at liquid helium temperature, both methods are proved valid. Additionally, it measures the thermal conductivity and the electric resistance of phosphor bronze screen stacks at room temperature and at low temperature. For electrically conductive contacts consisting of electrically conductive blocks and interposers such as indium foil, the thermal conductance at liquid helium temperature can be estimated with Wiedemann-Franz law when the temperature dependency of the properties is considered. In contrast, the thermal conductance of phosphor bronze stacks whose surface was oxidized could not be estimated with Wiedemann-Franz law between 4K and 300K.