Spectroscopic study of the radiation resistance of the plastic scintillator UPS-923A under γ- and electron irradiation

In this work, a spectroscopic investigation of the radiation resistance of the plastic scintillator UPS-923A under γ- and electron-irradiation was carried out. The scintillator is based on a polystyrene matrix doped with p-terphenyl (pTP) and diphenyloxazole-benzene (POPOP). Changes in the absorption and photoluminescence (PL) spectra of the samples after irradiation at various doses were examined. The results show that at low γ-irradiation doses (up to 10⁶ rad), the luminescence intensity of pTP increases, whereas that of POPOP decreases. At higher doses (≥10⁶ rad), degradation of both dopants and the polymer matrix is observed. Electron irradiation (fluence 10 ¹⁴–10 ¹⁶ e/cm²) produces a more destructive effect, leading to an irreversible decrease in PL intensity. The pTP molecule exhibits greater radiation resistance due to its stable aromatic structure, whereas POPOP, which contains oxazole rings, degrades more rapidly.