Thermal conductance measurement of the MAJIS insulating mountings down to cryogenic temperature

This paper summarizes the design implementation and validation of the measurement setup for the thermal characterization of the thermally insulating mountings of the MAJIS instrument. The challenges of the measurement derive from the low value of the conductance to be measured, in the range of few mW/K, the wide temperature range to be investigated, from 100 to 300 K, the need of operating under vacuum. The developed configuration exploits the guarded plate configuration to reduce the uncertainty on the parasitic heat fluxes, multilayer insulators to minimize the radiative heat exchange, a liquid nitrogen loop for the cooling of the heat sink. The setup has been built and validated with tests on a specimen to assess the repeatability of the measurement. With the characterization of different specimens from the same production batch the setup has allowed also assessing the repeatability of the manufacturing process.