Thermal neutron sensitive inorganic compound loaded thin-film composite plastic scintillators

The paper describes the preparation and characterization methodology of thermal neutron sensitive inorganic compound loaded polystyrene based thin-film Plastic Scintillators (PS). Inorganic compounds with thermal neutron sensitive elements such as B₂O₃, LiF, Gd₂O₂S:Tb, Gd₂O₃, Gd(BO₂)₃:Tb is loaded in plastic scintillators, at predetermined weight percentage in a solvent-based fabrication method. The PS base solution is prepared by dissolving required quantities of polystyrene, 2,5-Diphenyloxazole (PPO), 1,4-bis(5-Phenyloxazol-2-yl) Benzene (POPOP) in the p-xylene solvent. The loading material is mixed with the scintillator solution and coated over cellulose acetate-based transparency sheet. Thin sheets of 200 × 150 mm size and 250 ± 50 μm thickness PS are prepared through multiple coating. Photoluminescence (PL), Radioluminescence (RL) and pulse height spectra (PHS) of α, β, γ and neutron sources of the composite scintillators are studied. The selection of loading compounds is decided on their physical properties such as refractive index, the atomic percentage of neutron sensitive elements in the inorganic compound, band gap, and cost and availability of material. Gadolinium based compounds as a thermal neutron absorber showed higher detection capability for low-energy neutrons. Among the gadolinium loaded PS, Gd(BO₂)₃:Tb (14.3 wt%) composite scintillator showed the highest RL. A comprehensive analysis of PL, RL, PHS of α, pure β and γ sources, un-moderated and moderated Am-Be neutron source is discussed in the paper.