A SiPM-based ZnS:$^6$LiF scintillation neutron detector

TL;DR

This paper presents a neutron detection unit using a ZnS:$^6$LiF scintillator coupled with SiPMs and WLS fibers, achieving high efficiency and low background, suitable as a building block for multichannel neutron detectors.

Contribution

The work introduces a novel single-channel neutron detection module with optimized parameters, demonstrating its potential as a scalable component for advanced neutron scattering instruments.

Findings

Neutron detection efficiency of ~65% at 1.2 Å

Background count rate below 10^{-3} Hz

Gamma sensitivity less than 10^{-6}

Abstract

In the work presented here we built and evaluated a single-channel neutron detection unit consisting of a ZnS:$^6$LiF scintillator with embedded WLS fibers readout by a SiPM. The unit has a sensitive volume of 2.4 x 2.8 x 50 mm$^3$; 12 WLS fibers of diameter 0.25 mm are uniformly distributed over this volume and are coupled to a 1 x 1 mm$^2$ active area SiPM. We report the following performance parameters: neutron detection efficiency $\sim 65\,$% at $1.2\,\AA$, background count rate $< 10^{-3}$ Hz, gamma-sensitivity with $^{60}$Co source $< 10^{-6}$, dead time $\sim 20\,\mu$s, multi-count ratio $< 1\,$%. All these parameters were achieved up to the SiPM dark count rate of $\sim 2\,$MHz. We consider such detection unit as an elementary building block for realization of one-dimensional multichannel detectors for applications in the neutron scattering experimental technique. The dimensions of the unit and the number of embedded fibers can be varied to meet the specific application requirements. The upper limit of $\sim 2\,$MHz on the SiPM dark count rate allows to use SiPMs with larger active areas if required.