Study of a triple-discriminating plastic scintillator detector for fast neutrons, thermal neutrons, and gamma rays

Detecting fast and thermal neutrons plays a crucial role in neutrino experiments and reactor physics. In this study, we propose a plastic scintillator detector which demonstrates the ability to clearly distinguish fast neutrons, thermal neutrons, and gamma rays within mixed radiation fields, offering a practical approach for multi-radiation detection. Two plastic scintillator assemblies: EJ200+EJ426 and EJ276+EJ426 were setup, and the system energy response was calibrated using three gamma sources(137Cs, 22Na and 60Co). An Am-Be neutron source was employed, and pulse shape discrimination(PSD) was used to separate fast neutrons, thermal neutrons and gamma rays. Using a three-sigma discrimination criterion, the EJ200+EJ426 configuration was found to reliably distinguish thermal neutrons from gamma rays, while the EJ276+EJ426 configuration can effectively discriminate fast neutrons, thermal neutrons and gamma rays at gamma-equivalent energies above 1 MeV.