Photostimulated Luminescence and Thermoluminescence of LSO Scintillators

Photostimulated luminescence (PSL) and thermoluminescence (TL) from five Lu_(2(1-x))Ce_(2x)(SiO_4)O (LSO) crystals with different light outputs is reported. Optical irradiation into the Ce^(3+) absorption bands causes the appearance of a broad absorption band near 280 nm which is ascribed to Ce^(4+). In addition, a tail is observed extending beyond 700 nm. Optical irradiation into this tail (PSL) or heating of the crystal (TL) results in Ce^(3+) emission. It is shown that both PSL and TL are due to the same traps: In addition, an anti-correlation is found between the light output under gamma-ray irradiation and the trap concentration in the crystal. The nature of the recombination centers responsible for the low light output in some crystals is not clear. Annealing experiments suggest that the traps and the recombination centers may be related to oxygen vacancies.