Fast Neutron Detection with 6Li-loaded Liquid Scintillator

TL;DR

This paper presents the development and testing of a 6Li-loaded liquid scintillator detector for fast neutron detection, demonstrating its efficiency, capture lifetime, and pulse-shape discrimination capabilities through experimental data and Monte Carlo simulations.

Contribution

The paper introduces a novel 6Li-loaded liquid scintillator with micro-emulsion technology, and evaluates its performance for fast neutron detection and background reduction.

Findings

Effective neutron detection with 6Li-loaded scintillator

Comparable efficiency and capture lifetime to simulations

Successful pulse-shape discrimination between recoil types

Abstract

We report on the development of a fast neutron detector using a liquid scintillator doped with enriched Li-6. The lithium was introduced in the form of an aqueous LiCl micro-emulsion with a di-isopropylnaphthalene-based liquid scintillator. A Li-6 concentration of 0.15 % by weight was obtained. A 125 mL glass cell was filled with the scintillator and irradiated with fission-source neutrons. Fast neutrons may produce recoil protons in the scintillator, and those neutrons that thermalize within the detector volume can be captured on the Li-6. The energy of the neutron may be determined by the light output from recoiling protons, and the capture of the delayed thermal neutron reduces background events. In this paper, we discuss the development of this 6Li-loaded liquid scintillator, demonstrate the operation of it in a detector, and compare its efficiency and capture lifetime with Monte Carlo simulations. Data from a boron-loaded plastic scintillator were acquired for comparison. We also present a pulse-shape discrimination method for differentiating between electronic and nuclear recoil events based on the Matusita distance between a normalized observed waveform and nuclear and electronic recoil template waveforms. The details of the measurements are discussed along with specifics of the data analysis and its comparison with the Monte Carlo simulation.