Thermal modelling of coaxial line for cryogenic noise measurements

A numerical model is used for accurately calculating the temperature along a coaxial line with ends at different cryogenics temperatures. The calculations take into account the variation of thermal and electrical conductivity with temperature, an important consideration not present in previous publications. Estimates of line attenuation and added noise temperature can be more accurately calculated using this profile, and the profile can provide insight into thermal clamp position and thermal loading calculations. These calculations have a significant impact on the accuracy of variable temperature load and cold attenuator noise measurements.