As-grown color centers and radiation damage in Ce3+ -doped dense rare-earth orthoaluminate scintillators

Optical transmission and scintillation light yields were measured in Ce3+-doped LuAlO3 and (LuY)AlO3 solid solution single crystals grown by the vertical Bridgman and Czochralski processes. Depending on the growth history, the crystals exhibit dissimilar transmission properties in the UV range. The as-grown color centers possibly responsible for poor transmission properties in the range of Ce3+ emission were characterized by exposing non-activated crystals to 1 Mrad of 60Co gamma-rays. Radiation induced absorption in Ce3+-doped crystals is found to be higher in crystals with good initial transmission properties, while the crystals with high density of as-grown color centers are radiation hard. With time, partial slow-rate natural recovery from the damage was observed at room temperature in all studied crystals. Annealing at higher temperatures or optical bleaching contribute to recombination of gamma-ray induced color centers but affect inconsiderably the as-grown color centers.