The low-temperature energy calibration system for the CUORE bolometer array

TL;DR

This paper describes the design and development of a low-temperature energy calibration system for the CUORE bolometer array, addressing unique challenges to ensure precise calibration in a cryogenic environment for neutrinoless double beta decay search.

Contribution

It introduces a novel calibration system with moving gamma sources tailored for the CUORE cryogenic setup, ensuring minimal heat load and contamination risk.

Findings

Design successfully integrates sources into cryostat

Expected to provide accurate energy calibration

Addresses heat load and radiopurity constraints

Abstract

The CUORE experiment will search for neutrinoless double beta decay (0nDBD) of 130Te using an array of 988 TeO_2 bolometers operated at 10 mK in the Laboratori Nazionali del Gran Sasso (Italy). The detector is housed in a large cryogen-free cryostat cooled by pulse tubes and a high-power dilution refrigerator. The TeO_2 bolometers measure the event energies, and a precise and reliable energy calibration is critical for the successful identification of candidate 0nDBD and background events. The detector calibration system under development is based on the insertion of 12 gamma-sources that are able to move under their own weight through a set of guide tubes that route them from deployment boxes on the 300K flange down into position in the detector region inside the cryostat. The CUORE experiment poses stringent requirements on the maximum heat load on the cryostat, material radiopurity, contamination risk and the ability to fully retract the sources during normal data taking. Together with the integration into a unique cryostat, this requires careful design and unconventional solutions. We present the design, challenges, and expected performance of this low-temperature energy calibration system.