Studies of blue light induced phototransferred thermoluminescence in CaSO4:Mg

Abstract

In this work, phototransferred thermoluminescence (PTTL) was observed in polycrystalline powder samples of Mg-doped CaSO4 (CaSO4:Mg) which were produced via the precipitation technique. The thermoluminescence (TL) glow curve showed the two separate main peaks. Composition of the peaks was at 90, 145, 180 and 235 degrees C and on the high temperature side, at 355, 410 and 475 degrees C with a 5 degrees C/s heating rate after delivering 100 Gy beta dose. The PTTL induced in CaSO4:Mg using blue light (470 nm) was reported and some PTTL characteristics were investigated. The PTTL intensity as a function of duration and temperature of illumination was recorded. As a function of increasing beta dose, a linear dose-response was obtained for the sample at 100 degrees C within the dose range from 1 to 150 Gy. The decaying of the PTTL signals of the previously irradiated sample was examined through successive blue light stimulation cycles. PTTL was used to determine dark fading of the material which was found stable with 2% loss of charge in the deep traps accessed by the PTTL measurement procedure. The thermal activation energy of the source traps involved in the PTTL was evaluated as 1.90 eV using the pulse annealing technique. Although these results showed that CaSO4:Mg presented a good PTTL performance and the blue light-induced PTTL signal can be used for dosimetry, it needs further study to understand the physical mechanisms associated with the transfer of charge from the deep traps probed by the PTTL measurements.