The specific heat and thermal conductivity of Eccosorb CR-124 between 800mK and 6K

Eccosorb CR-124 is a castable iron-loaded epoxy resin with excellent absorption properties for electromagnetic waves in the GHz range. It is commonly used in low temperature instruments to absorb thermal radiation. The specific heat c ( T ) of Eccosorb CR-124 was measured between 800 mK and 6 K with the heat pulse method. The results were fitted to the function c ( T ) = ( 0.132 ± 0.003 ) · T + ( 0.0053 ± 0.0003 ) · T 3 J kg - 1 K - 1 , with T being the temperature in Kelvin. In addition, the thermal diffusivity D ( T ) of Eccosorb CR-124 was determined. At a temperature of 2.3 K, a peak is observed in D ( T ) . Consequently, the thermal conductivity λ ( T ) of Eccosorb CR-124 features two distinct regimes. Below 2.3 K, it fits the function λ ( T 2.3 K ) = ( 0.0038 ± 0.0003 ) · T 2 ± 0.1 W m - 1 K - 1 . Above 2.3 K, it fits the function λ ( T > 2.3 K ) = ( 0.0057 ± 0.0004 ) · T 1.4 ± 0.04 W m - 1 K - 1 .