Development Of A Polystyrene-based N/γ Discrimination Plastic Scintillator Detector

Neutron detection is a key technology for mankind to understand the cosmos and micro world;in the sites of those occuring nuclear fission and nuclear fusion transient nuclear processes,such as decommissioned nuclear facilities and radioactive waste,fusion reactors,nuclear explosion tests,nuclear power plants and spallation neutron source devices,the occasion of measuring neutrons is usually to be accompanied by the interference of gamma ray background,so neutron detection involves n/γdiscrimination technology under strong gamma background radiation.n/γdiscrimination,mainly use three types of detectors which are single crystal scintillators,liquid scintillators and organic plastic scintillators that have the advantages of low-cost and large-size preparation.However,the existing organic plastic scintillator neutron detectors have not yet equipped with high n/γpulse shape discrimination capability and also can not be used for the comprehensive performance of precise measurement of time and energy spectrum of neutrons in a wide energy range.Therefore,it is of great significance to develop new plastic scintillator detectors with high luminescence yield,fast time resolution,wide energy range of neutrons,high sensitive detection ability,low production cost,and high n/γdiscrimination ability.This project is oriented to the needs of the Chinese Spallation Neutron Source（CSNS）device in the back-angle white light neutron source line station（Back-n）neutron beam monitoring needs,and develops a set of detectors that can be applied to a strong mixed pulse radiation field,with both wide energy range of neutrons and well n/γdiscrimination ability.The main research contents and conclusions are as follows:（1）The polystyrene matrix material is doped with a high-weight fraction primary fluorescent dye PPO and a secondary fluorescent dye DPA with high luminescence quantum yield to prepare a new type of n/γdiscrimination plastic scintillator detector;spectral analysis measurement shows the self-absorption effect of the prepared scintillator is rarely,and the scintillation fluorescence can be efficiently transferred between the substrate and the fluorescent dye;the n/γdiscrimination performance of the scintillator is tested by using the ²⁵²Cf isotope radiation source and the high voltage D+T fusion neutron beam accelerator of the Chinese Institute of Atomic Energy.The prepared scintillator has excellent n/γdiscrimination ability in the 1-15 Me V neutron energy region,and the quality factor FOM value that characterizes its discrimination ability can reach more than 1.30,which is equivalent or even better than that of the commercial EJ-276 under the same conditions.（2）Using polystyrene as the matrix,doped with the primary fluorescent dye TPB,the secondary fluorescent dye DCM and the rare earth fluorescent dye Eu（DBM）-₃phen,a plastic scintillator with a metal ligand as the luminescent center was researched and prepared.Tests of fluorescence emission spectroscopy,photoluminescence attenuation,and quantum yield show that TPB and DCM fluorescent dyes have good spectral matching,and the prepared plastic scintillator has better spectral performance if the mass fraction concentration of Eu（DBM）₃phen,TPB,DCM are reached at 3.0 wt%,2.0wt%,0.04wt%respectively.However,preliminary particle detection experimental measurements show that the scintillator does not show n/γdiscrimination ability.In order to demonstrate the efficient transfer function of the metal ligand in the fluorescence energy transfer process of the scintillator,It is necessary to further optimize the scintillator components and their concentration ratios.