The ASTAROTH project

TL;DR

The ASTAROTH project aims to improve dark matter detection by using SiPMs instead of traditional PMTs in NaI(Tl) detectors, enabling lower noise and energy thresholds in cryogenic conditions.

Contribution

It introduces a novel all-active detector design with SiPMs operating at cryogenic temperatures to enhance dark matter search sensitivity.

Findings

Successful characterization of SiPM and crystal response at low temperatures.

First operation of NaI(Tl) crystal read by SiPM in cryogenic conditions.

Potential for lower background noise and energy thresholds in dark matter detection.

Abstract

The most discussed topic in direct search for dark matter is arguably the verification of the DAMA claim. In fact, the observed annual modulation of the signal rate in an array of NaI(Tl) detectors can be interpreted as the awaited signature of dark matter interaction. Several experimental groups are currently engaged in the attempt to verify such a game-changing claim with the same target material. However, all present-day designs are based on a light readout via Photomultiplier Tubes, whose high noise makes it challenging to achieve a low background in the 1-6 keV energy region of the signal. Even harder it would be to break below 1 keV energy threshold, where a large fraction of the signal potentially awaits to be uncovered. ASTAROTH is an R\&D project to overcome these limitations by using Silicon Photomultipliers (SiPM) matrices to collect scintillation light from NaI(Tl). The all-active design based on cubic crystals is operating in the 87-150 K temperature range where SiPM noise can be even a hundred times lower with respect to PMTs. The cryostat was developed following an innovative design and is based on a copper chamber immersed in a liquid argon bath that can be instrumented as a veto detector. We have characterized separately the crystal and the SiPM response at low temperature and we have proceeded to the first operation of a NaI(Tl) crystal read by SiPM in cryogeny.