Intrinsic radiation background of LaBr$_3$(Ce) detector via coincidence measurements and simulations

TL;DR

This study quantifies the intrinsic radiation background of LaBr3(Ce) detectors using coincidence measurements and simulations, identifying key isotopes contributing to background noise and providing activity levels for improved low-background applications.

Contribution

It combines experimental coincidence measurements with Geant4 simulations to accurately identify and quantify the intrinsic radioisotope activities in LaBr3(Ce) detectors, a novel approach for background assessment.

Findings

Main background activity is 1.480 Bq/cm^3, primarily from 138La.

Identified isotopes include 138La, 211Bi, 219Rn, 223Ra, and 227Th.

Quantified specific activities of each isotope in the detector.

Abstract

The LaBr$_3$(Ce) detector has attracted much attention in recent years for its superior characteristics to other scintillating materials in terms of resolution and efficiency. However, it has relatively high intrinsic radiation background due to the naturally occurring radioisotope in lanthanum, actinium and their daughter nuclei. This limits its applications in low counting rate experiments. In this paper, we identified the radioactive isotopes in the $\phi3''\times 3''$ Saint-Gobain B380 detector by a coincidence measurement using a Clover detector in a low-background shielding system. Moreover, we carried out a Geant4 simulation to the experimental spectra to evaluate the activities of the main internal radiation components. % by means of the $\alpha$, $\gamma$ and $\beta$ decays from the $^{138}$La and $^{227}$Ac. The activity of radiation background of B380 is determined to be 1.480 (69) Bq/cm$^3$, the main sources of which include $^{138}$La of 1.425 (59) Bq/cm$^3$, $^{211}$Bi of 0.0136 (15) Bq/cm$^3$, $^{219}$Rn of 0.0125 (17) Bq/cm$^3$, $^{223}$Ra of 0.0127 (14) Bq/cm$^3$, and $^{227}$Th of 0.0158 (22) Bq/cm$^3$.