A Thermal Model of Low-Temperature Light Detectors for Neutrinoless Double Beta Decay Experiments

We report a detector model study for light detectors having Ge and Si wafers as absorbers with a metallic magnetic calorimeter (MMC) readout. The model explains the heat flow processes between the thermal components in the detector system, including athermal and thermal phonon transfers and electronic heat diffusion. The temperature dependence of the thermal conductance values was in good agreement with their expectations. The analysis also resulted in finding the characteristic time constants of the athermal phonons for direct absorption in the phonon collector film and for the downconversion to thermal phonons of the absorber wafers. It is a complete detector model to be applied for various detector variations such as the type and dimensions of the wafer absorber.