Characterization of a CsI(Tl) Scintillator Coupled to a SiPM at Cryogenic Temperatures

TL;DR

This study characterizes a CsI(Tl) scintillator coupled with a SiPM at cryogenic temperatures, demonstrating optimal detection performance at 175 K for low-energy particle detection and rare-event searches.

Contribution

It provides the first detailed characterization of a CsI(Tl) scintillator with SiPMs at cryogenic temperatures, highlighting optimal temperature for detection efficiency.

Findings

Maximum figure of merit at 175 K indicating optimal efficiency

Baseline resolution of ~1 keV at 175 K

Effective detection threshold of ~3 keV

Abstract

We report on the scintillation characterization of a 1 cm^3 CsI(Tl) crystal coupled to a 6 x 6 mm^2 SiPM read out with a custom transimpedance amplifier at cryogenic temperatures. The crystal was prepared with optical-grade surfaces and enclosed in a multi layer shielding system to suppress ambient light and background radiation. The detector response was studied at temperatures ranging from 100 K to room temperature. A figure of merit, defined as the ratio of the 59.5 keV peak position to the baseline resolution, showed a maximum at 175 K, indicating optimal photon detection efficiency. Pulse shape analysis demonstrated temperature-dependent variations in scintillation decay. At 175 K, the baseline resolution was sigma ~ 1 keV, corresponding to an effective threshold of ~ 3 keV. These results confirm the capability of the CsI(Tl) SiPM system to operate at low thresholds for rare-event searches and low-energy particle detection.