An Energy-dependent Electro-thermal Response Model of CUORE Cryogenic Calorimeter

TL;DR

This paper develops a detailed non-linear electro-thermal model for CUORE cryogenic calorimeters, improving understanding of detector response and pulse shape behavior to enhance sensitivity in neutrinoless double-beta decay searches.

Contribution

It introduces an empirical correction to the thermistor model and demonstrates improved agreement with detector data, advancing thermal modeling of cryogenic calorimeters.

Findings

The empirical correction improves pulse shape modeling up to 6 MeV.

Intrinsic thermal noise is negligible compared to observed noise.

The model captures energy-dependent pulse shapes more accurately.

Abstract

The Cryogenic Underground Observatory for Rare Events (CUORE) is the most sensitive experiment searching for neutrinoless double-beta decay ($0\nu\beta\beta$) in $^{130}\text{Te}$. CUORE uses a cryogenic array of 988 TeO$_2$ calorimeters operated at $\sim$10 mK with a total mass of 741 kg. To further increase the sensitivity, the detector response must be well understood. Here, we present a non-linear thermal model for the CUORE experiment on a detector-by-detector basis. We have examined both equilibrium and dynamic electro-thermal models of detectors by numerically fitting non-linear differential equations to the detector data of a subset of CUORE channels which are well characterized and representative of all channels. We demonstrate that the hot-electron effect and electric-field dependence of resistance in NTD-Ge thermistors alone are inadequate to describe our detectors' energy dependent pulse shapes. We introduce an empirical second-order correction factor in the exponential temperature dependence of the thermistor, which produces excellent agreement with energy-dependent pulse shape data up to 6 MeV. We also present a noise analysis using the fitted thermal parameters and show that the intrinsic thermal noise is negligible compared to the observed noise for our detectors.