Pulse Shape Discrimination of low-energy nuclear and electron recoils for improved particle identification in NaI:Tl

TL;DR

This paper introduces a new pulse shape discrimination method for NaI:Tl crystals that improves the identification of nuclear versus electron recoils at low energies, enhancing particle detection accuracy.

Contribution

A novel likelihood-based PSD approach is proposed, outperforming traditional mean-time methods and combining techniques for better discrimination in low-energy events.

Findings

Likelihood-based PSD outperforms charge-weighted mean-time

Combining PSD methods enhances discrimination power

Effective at energies between 2 and 40 keV

Abstract

The scintillation mechanism in NaI:Tl crystals produces different pulse shapes that are dependent on the incoming particle type. The time distribution of scintillation light from nuclear recoil events decays faster than for electron recoil events and this difference can be categorised using various Pulse Shape Discrimination (PSD) techniques. In this study, we measured nuclear and electron recoils in a NaI:Tl crystal, with electron equivalent energies between 2 and 40 keV. We report on a new PSD approach, based on an event-type likelihood; this outperforms the charge-weighted mean-time, which is the conventional metric for PSD in NaI:Tl. Furthermore, we show that a linear combination of the two methods improves the discrimination power at these energies.