Performance of a segmented $^{6}$Li-loaded liquid scintillator detector for the PROSPECT experiment

TL;DR

This paper presents the design and performance evaluation of a 50-liter $^{6}$Li-loaded liquid scintillator detector prototype for the PROSPECT experiment, demonstrating high light collection, good energy resolution, and effective neutron detection capabilities.

Contribution

The paper introduces a prototype detector with optimized design features that meet PROSPECT's requirements and showcases its performance metrics and stability.

Findings

High light collection of 850 PE/MeV achieved

Energy resolution of 4.0% at 1 MeV demonstrated

Efficient pulse-shape discrimination and neutron capture detection

Abstract

This paper describes the design and performance of a 50 liter, two-segment $^{6}$Li-loaded liquid scintillator detector that was designed and operated as prototype for the PROSPECT (Precision Reactor Oscillation and Spectrum) Experiment. The two-segment detector was constructed according to the design specifications of the experiment. It features low-mass optical separators, an integrated source and optical calibration system, and materials that are compatible with the $^{6}$Li-doped scintillator developed by PROSPECT. We demonstrate a high light collection of 850$\pm$20 PE/MeV, an energy resolution of $\sigma$ = 4.0$\pm$0.2% at 1 MeV, and efficient pulse-shape discrimination of low $dE/dx$ (electronic recoil) and high $dE/dx$ (nuclear recoil) energy depositions. An effective scintillation attenuation length of 85$\pm$3 cm is measured in each segment. The 0.1% by mass concentration of $^{6}$Li in the scintillator results in a measured neutron capture time of $\tau$ = 42.8$\pm$0.2 $\mu s$. The long-term stability of the scintillator is also discussed. The detector response meets the criteria necessary for achieving the PROSPECT physics goals and demonstrates features that may find application in fast neutron detection.