Long-Term Stability of Underground Operated CZT Detectors Based on the Analysis of Intrinsic $^{113}$Cd \beta$^{-}$-Decay

TL;DR

This study demonstrates that CZT detectors used in underground experiments for neutrinoless double beta-decay can operate reliably over long periods, with intrinsic $^{113}$Cd decay serving as a stable internal performance monitor.

Contribution

It provides evidence of the long-term stability of CZT detectors and introduces the use of intrinsic $^{113}$Cd decay as an internal stability indicator.

Findings

CZT detectors operated stably for over three years

Intrinsic $^{113}$Cd decay can monitor detector performance

Detectors collected 218 kg·days of data

Abstract

The COBRA collaboration operates a demonstrator setup at the underground facility LNGS (Laboratori Nazionali del Gran Sasso, located in Italy) to prove the technological capabilities of this concept for the search for neutrinoless double beta-decay. The setup consists of 64 $(1\times\!1\times\!1)$ cm$^{3}$ CZT detectors in CPG configuration. One purpose of this demonstrator is to test if reliable long-term operation of CZT-CPG detectors in such a setup is possible. The demonstrator has been operated under ultra low-background conditions since more than three years and collected data corresponding to an exposure of 218 kg$\cdot$days. The presented study focuses on the long-term stability of CZT detectors by analyzing the intrinsic, fourfold forbidden non-unique $^{113}$Cd single beta-decay. It can be shown that CZT detectors can be operated stably for long periods of time and that the $^{113}$Cd single beta-decay can be used as an internal monitor of the detector performance during the runtime of the experiment.