Stabilization Heaters for Low-Temperature Thermal Calorimeters

Abstract

Signal amplitudes of low-temperature detectors, vastly used in rare-event searches such as neutrinoless double beta decay experiments, are sensitive to measurement conditions causing instability such as operation temperature fluctuations. Those detector signal amplitudes thus present drifts and shifts over time due to those temperature fluctuations and need to be corrected. This effect degrades the energy resolution and particle discrimination capabilities of the calorimetric detection at low temperatures, with both strongly affecting the sensitivity of rare-event search experiments. Joule heaters were developed and used on absorber crystals in the Advanced Mo-based Rare process Experiment project, to inject periodically a controlled amount of heat, and thus produce reference signals that can be used to correct and thus stabilize the signal amplitudes of the detectors. The pulse height of the heater signals could not be used as a correction parameter as it was affected by various sources of instability. Instead, the rise time of the heater signals was used to generate a correction function describing well the time dependence of the particle-induced events in the crystals and thus provided a significant improvement of the energy resolution and particle discrimination capabilities to separate $\beta /\gamma$ and $\alpha$ events.