Discrimination of fast neutrons, thermal neutrons, and γ rays in mixed radiation fields is important for radiation monitoring, reactor-related measurements, and background suppression in nuclear experiments. In this work, we investigate a compact plastic-scintillator sensor composed of EJ276 or EJ200 optically coupled to an EJ426 thermal neutron screen and read out by a single photomultiplier tube (PMT). The γ equivalent energy response of the detector assemblies was calibrated using 137Cs, 22Na, and 60Co sources through Compton edge analysis, and pulse shape discrimination was evaluated with an AmBe neutron source under different moderator thicknesses. The EJ200+EJ426 assembly provides a well separated discrimination between thermal-neutron capture events and γ dominated events over the measured range, with a figure of merit greater than 5. In contrast, the EJ276+EJ426 assembly produced three identifiable signal populations associated with γ rays, fast neutrons, and thermal neutrons. These results show that the proposed sensor architecture is a promising compact approach for mixed field radiation applications
@article{arxiv.2512.15585,
title = {Performance Characterization of a Plastic-Scintillator Sensor for Fast-Neutron, Thermal-Neutron, and Gamma-Ray Discrimination},
author = {Yuhang Liu and Fengpeng An and Guang Luo and Wei Wang and Xuesong Zhang and Dixiao Lu and Xiaohao Yin},
journal= {arXiv preprint arXiv:2512.15585},
year = {2026}
}