Low energy fast events from radon progenies at the surface of a CsI(Tl) scintillator

TL;DR

This paper investigates alpha decays from radon progenies on CsI(Tl) scintillator surfaces, revealing their unique fast signals that can be distinguished from neutron and gamma backgrounds, aiding rare event searches.

Contribution

It demonstrates that surface radon progeny alpha decays produce distinct fast signals in CsI(Tl) scintillators, improving background discrimination in rare event detection.

Findings

Alpha decays produce characteristic fast signals.

Surface contamination impacts background signals.

Distinct mean-time distribution helps identify radon progenies.

Abstract

In searches for rare phenomena such as elastic scattering of dark matter particles or neutrinoless double beta decay, alpha decays of Rn222 progenies attached to the surfaces of the detection material have been identified as a serious source of background. In measurements with CsI(Tl) scintillator crystals, we demonstrate that alpha decays of surface contaminants produce fast signals with a characteristic mean-time distribution that is distinct from those of neutron- and gamma-induced events.