First operation of undoped CsI directly coupled with SiPMs at 77 Kelvin

TL;DR

This study demonstrates the successful operation of undoped CsI crystal coupled with SiPMs at 77 Kelvin, achieving high light yield and highlighting its potential for neutrino and dark matter detection, despite some technical challenges.

Contribution

First demonstration of undoped CsI with SiPMs at cryogenic temperatures, showing promising light yield for rare-event detection applications.

Findings

Light yield of 43.0 ± 1.1 PE/keV at 77 K

Potential for neutrino and dark matter detection

Identified challenges like energy resolution and optical cross-talk

Abstract

The light yield of a small undoped cesium iodide (CsI) crystal directly coupled with two silicon photomultipliers (SiPMs) at about 77~Kelvin was measured to be $43.0 \pm 1.1$~photoelectrons (PE) per keV electron-equivalent (keV$_\text{ee}$) using $X$ and $\gamma$-ray peaks from an $^{241}$Am radioactive source from 18 to 60 keV. The high light yield together with some other technical advantages illustrate the great potential of this novel combination for neutrino and low-mass dark matter detection, particularly at accelerator-based neutrino sources, where random background can be highly suppressed by requiring coincident triggers between SiPMs and beam pulse timing signals. Some potential drawbacks of using cryogenic SiPMs instead of photomultiplier tubes (PMTs) were identified, such as worse energy resolution and optical cross-talks between SiPMs. Their influence to rare-event detection was discussed and possible solutions were provided.