Thermal conductivity measurements of PTFE and Al$_2$O$_3$ ceramic at sub-Kelvin temperatures

TL;DR

This study measures the thermal conductivities of PTFE and Al₂O₃ ceramic at sub-Kelvin temperatures, providing essential data for designing low-temperature bolometric detectors used in rare event searches.

Contribution

The paper presents new measurements of PTFE and Al₂O₃ thermal conductivities at sub-Kelvin temperatures, including detailed temperature dependencies and measurement techniques.

Findings

PTFE exhibits quadratic temperature dependence from 0.17 to 0.43 K.

Al₂O₃ shows cubic dependence above ~0.3 K and linear below.

Results inform material selection for low-temperature detectors.

Abstract

The design of low temperature bolometric detectors for rare event searches necessitates careful selection and characterization of structural materials based on their thermal properties. We measure the thermal conductivities of polytetrafluoroethylene (PTFE) and Al$_2$O$_3$ ceramic (alumina) in the temperature ranges of 0.17-0.43 K and 0.1-1.3 K, respectively. For the former, we observe a quadratic temperature dependence across the entire measured range. For the latter, we see a cubic dependence on temperature above ~0.3 K, with a linear contribution below that temperature. This paper presents our measurement techniques, results, and theoretical discussions. Keywords: Thermal Conductivity, PTFE, Al$_2$O$_3$ ceramic, Bolometer