Light yield of an undoped CsI crystal coupled directly to a photomultiplier tube at 77 Kelvin

TL;DR

This study demonstrates a record-high light yield of undoped CsI crystals at 77 Kelvin when coupled directly to a photomultiplier tube, potentially enhancing dark matter detection sensitivity.

Contribution

It reports the highest light yield achieved with undoped CsI crystals at cryogenic temperature, introducing a promising technique for low-threshold dark matter and neutrino experiments.

Findings

Achieved 20.4 photoelectrons/keV light yield at 77 K

Lower energy detection threshold possible with this method

Measured scintillation decay constants consistent with literature

Abstract

A light yield of 20.4 $\pm$ 0.8 photoelectrons/keV was achieved with an undoped CsI crystal coupled directly to a photomultiplier tube at 77 Kelvin. This is by far the largest yield in the world achieved with CsI crystals. An energy threshold that is several times lower than the current dark matter experiments utilizing CsI(Tl) crystals may be achievable using this technique. Together with novel CsI crystal purification methods, the technique may be used to improve the sensitivities of dark matter and coherent elastic neutrino-nucleus scattering experiments. Also measured were the scintillation light decay constants of the undoped CsI crystal at both room temperature and 77 Kelvin. The results are consistent with those in the literature.