Pereymak V. Development of plastic scintillator for neutron-gamma discrimination

This thesis is devoted to creation of plastic scintillators (PS) for neutron-gamma discrimination applying different activation additives. A PS for neutron-gamma discrimination with realization of the spin-orbit coupling mechanism is created. This PS has two radiating centers: the first is a metal organic complex dibenzoylmethane-1,10-phenanthroline europium (Eu[DBM]3Phen), which converts predominantly the triplet excited states energy to radiation, and the second - 1,4-dimethyl-9,10-diphenylanthracene (DMDPA), which converts to radiation only the singlet excited states energy. The FOM of the given PS is equal to 1.37 in the wide energy diapason. Also, PS for neutron-gamma discrimination with realization of the triplet-triplet annihilation mechanism. This mechanism is realized by input of scintillation additives into the PS content in the high concentration. This leads to degradation of the PS scintillation and mechanical properties while certain time. Thus, PS for neutron-gamma discrimination, containing scintillation additives with the suppressed diffusion: meta-dimethyl-2,5-diphenyl-1,3,4-oxadiazole (m-DMPPD), tert-butyl-2,5-diphenyl-1,3,4-oxadiazole (TBPPD), 2-phenyl-5-(4-t-butylphenyl)-1,3,4-oxazole (TBPPO) were created, which haven't got these drawbacks. Their neutron-gamma discrimination parameter and microhardness were measured. The neutron-gamma discrimination parameter FOM for the PS with m-DMPPD, TBPPD, TBPPO is equal to 1.53, 2.0 і 2.12, respectively. The microhardness for the PS with m-DMPPD, TBPPD, TBPPO is equal to 73, 135 і 38.8 MPa, respectively. The given PS are polymerized in big volumes (samples with 50 mm in diameter and 50 mm in height) and have the high long-term stability.