Effects of Gamma-Induced Defects on the Activator Glow in the Lu2SiO5:Ce Scintillator Crystals

Correlations between the optical absorption spectra and integral thermal glow curves (300–600 K) of the Lu2SiO5:Ce scintillator crystals irradiated by 60Co gamma quanta with energies of 1.17 and 1.33 MeV at a dose rate of 1.1 Gy/s in the dose range of 70–5 × 107 Gy at a temperature of 310 K and their gamma luminescence have been investigated. The intrinsic defects before irradiation, including the neutral VO5 centers with an absorption band of 193 nm, ≡Si–VO5 (213 nm), Lu1–F+–Si (238 nm), Ce3+/Ce4+ (263 nm), as well as the Ce3+/F (295 nm) centers are generated during the technological process. Irradiation with doses of up to 5 × 104 Gy reduces the concentration of the VO5 centers, but does not affect the other centers. However, at doses of more than 5 × 104 Gy, the concentration of all the other defects in the LSO:Ce structure increases. The recovery of an optical absorption band of 193 nm and a decrease in the intensity of the thermal glow peak at 335 K with increasing time (1, 3, and 10 h) of exposure at 305 K, as well as the correlated growth of the optical absorption at 238 nm and the thermal glow peak at 540 K after irradiation with doses from 70 to 2.3 × 106 Gy are related to the release of electrons from these color centers and radiative recombination at the Ce1 centers. A decrease in the Ce3+ gamma luminescence yield in bands of 400 and 420 nm at doses of more than 105 Gy is possibly due to an increase in the concentration of the ≡Si–VO4, Lu1–F+–Si, and Ce3+/F centers competing with the Ce1 centers in trapping electrons. In this way, the upper limit of stability of the Lu2SiO5:Ce gamma scintillator (105 Gy) has been determined.

Перевод пока недоступен