Solvents with different moisture levels: Critical impact factors on fluorescence-scintillation properties of liquid scintillators

Liquid scintillator consists of an organic solvent and one or more scintillation solutes, which can emit light pulses after absorbing X- and γ-rays, or high-energy particles. It has the characteristics of strong neutron/γ-ray (n/γ) discrimination, short decay time, unlimited size and low cost, which plays an important role in high-sensitivity and large-scale radiation detection, especially in the construction and safe operation of nuclear facilities. However, the impact of solvent selection and moisture content on the fluorescence-scintillation properties of scintillators has not been adequately investigated in the literature. In this study, liquid scintillators consisting of scintillation solutes, 2, 5-diphenyl-oxazole and 1, 4-bis (5-phenyl-2-oxazolyl) benzene, were prepared with different moisture contents, which were determined using the Karl-Fischer method. The fluorescence emission spectra, scintillation sensitivity and n/γ discrimination were systematically characterized using various solvents with corresponding moisture contents. The results show that the scintillation count rate and n/γ discrimination reach their maximum values when employing p-xylene as the solvent and maintaining moisture content below 20 ppm. The theoretical calculation elucidates the performance degradation of liquid scintillators induced by moisture.