Pulse-shape discrimination and energy quenching of alpha particles in Cs$_2$LiLaBr$_6$:Ce$^{3+}$

TL;DR

This study investigates the pulse-shape discrimination and energy quenching of alpha particles in the Cs$_2$LiLaBr$_6$:Ce$^{3+}$ scintillator, revealing its ability to distinguish alpha backgrounds and quantifying alpha quenching behavior.

Contribution

The paper provides the first detailed analysis of alpha particle pulse-shape discrimination and quenching in CLLB, including intrinsic alpha background characterization and a linear quenching model.

Findings

Pulse-shape discrimination with a figure of merit of 0.98.

Linear quenching relationship for alpha particles above 5 MeV.

Intrinsic alpha background attributed to actinium contamination.

Abstract

Cs$_2$LiLaBr$_6$:Ce$^{3+}$ (CLLB) is an elpasolite scintillator that offers excellent linearity and gamma-ray energy resolution and sensitivity to thermal neutrons with the ability to perform pulse-shape discrimination (PSD) to distinguish gammas and neutrons. Our investigation of CLLB has indicated the presence of intrinsic radioactive alpha background that we have determined to be from actinium contamination of the lanthanum component. We measured the pulse shapes for gamma, thermal neutron, and alpha events and determined that PSD can be performed to separate the alpha background with a moderate figure of merit of 0.98. We also measured the electron-equivalent-energy of the alpha particles in CLLB and simulated the intrinsic alpha background from $^{227}$Ac to determine the quenching factor of the alphas. A linear quenching relationship $L_{\alpha} = E_{\alpha} \times q + L_0$ was found at alpha particle energies above 5 MeV, with a quenching factor $q = 0.71$ MeVee/MeV and an offset $L_0 = - 1.19$ MeVee.