Luminescence and Defects in Ca2+ Doped Thoria Crystals

Abstract

The luminescence emitted during X-irradiated (XL) as well as the thermoluminescence (TL) of single ThO2:Ca crystals were studied. Results were compared to those obtained for pure Thoria crystals.[1] The TL was excited at 80 K by X or monochromatic vacuum-ultraviolet (vuv) radiation and excitation spectra were measured between 130 and 250 nm. Measured were also the spectral composition of the emission and the temperature dependence of the main XL emission bands. Results show that after uv irradiation TL peaks appeared at the same temperatures and with the same activation energies as after X-irradiation and after self excitation of the radioactive material, indicating that they are due to the same defects. The absorption edge of ThO2 is at about 213 nm. The excitation spectrum of ThO2:Ca showed maxima at 146, 163, 170 and 183 nm. Essentially the same maxima were recorded for pure ThO2.