Pulse-shape discrimination in water-based scintillators

TL;DR

This paper introduces water-based liquid scintillators capable of effectively discriminating between neutron and gamma-ray interactions, with promising light yield and discrimination performance suitable for radiation detection applications.

Contribution

The study develops stable water-in-oil emulsions with optimized scintillation properties and demonstrates their neutron/gamma discrimination capabilities, advancing water-based scintillator technology.

Findings

Achieved up to 18% of the light yield of traditional scintillators.

Demonstrated a neutron/gamma discrimination figure of merit of 1.79.

Optimized emulsion composition with 33 wt.% scintillating oil.

Abstract

This work describes a class of liquid scintillators that contain mostly water (>50 wt. % of the entire composition) and can discriminate between interactions induced by neutrons and gamma rays. By balancing the interface interactions between the components of the formulation, these scintillators form emulsions that can be thermodynamically stable. This approach, which considers a quantity known as the hydrophilic-lipophilic difference, requires consideration of the salinity and temperature as well as characterization of the surfactants and oil phase. Emulsions comprised of water and various oils were characterized first. Then, the effect of scintillating dyes in the oil phase was considered, followed by the construction of partial phase diagrams of the emulsions. For transparent oil-in-water emulsions with a single phase, the scintillation light yield and properties of pulse-shape discrimination were measured. The best performing scintillators contained 33 wt. % of a scintillating oil phase and exhibited a light yield that was as high as 18% of the light yield of a commercially available liquid scintillator that does not contain water (EJ-309). These water-based liquid scintillators exhibited a figure of merit of neutron/gamma ray discrimination as high as 1.79 at about 1500 keVee.