Measurement of thermophysical properties of polyimide and a black paint for future development of cryogenic radiometers

We have measured the thermal conductivity of polyimide rod at temperatures from 2.4 K to 8 K, and the specific heats of polyimide rod and a black pain t at 2.4 K and 4.4 K. It is shown that the responsivity and time constant o f cryogenic radiometers can be significantly improved by the use of a polyi mide film as the heat link. This study will help future development of high ly sensitive absolute cryogenic radiometers.