High performance thermal link with small spring constant for cryogenic applications

We developed a soft and high thermal conductive thermal link for cryogenic applications. The measured maximum thermal conductivity was approximately 18500 W/m/K at 10 K. This spring constant was 1/43 of that of a single thick wire with the same cross-sectional area at room temperature. We reached these performances by utilizing high purity aluminum (99.9999%, 6 N) and by stranding many thin wires that are 0.15 mm in diameter. The electrical Residual Resistivity Ratio was also measured and used to estimate the thermal conductivity by the Wiedemann–Franz law. We observed the size effect on the electrical conductivity, and evaluated the effect of mechanical deformation to the RRR. These evaluations allow us to design a pragmatic thermal link for cryogenic application.