The effect of pre-irradiation annealing on the thermoluminescence of LiF:Mg, Cu, P phosphor grown by EFG technique

Abstract

LiF crystal doped with magnesium (Mg), copper (Cu) and phosphorous (P) was grown in the form of multicrystalline sheet using Edge-defined film-fed growth (EFG) technique for dosimetry application. These crystals were grown in argon gas atmosphere using graphite crucible and stainless steel die. Dosimetry peak was observed at 210 °C for as-grown crystal. As reported earlier LiF:Mg, Cu, P is a highly sensitive material but losses its sensitivity if annealed at temperature above 240 °C. In this paper, the effect of annealing temperature on thermoluminescence glow-curve structure, maximum peak temperature, peak height and integrated area of the glow peak of EFG grown samples was investigated in detail. Annealing temperature range from 220 °C to 500 °C was considered for the study. Experimental results of the obtained glow curve show that with increase in annealing temperature, glow peak shift towards higher temperature region with substantial increase in TL intensity. Annealing at 500 °C for 10 min gave maximum TL intensity with main dosimetry peak positioned at 233 °C. Change in the defect structure with different pre-annealing temperature was analysed using trapping parameters. ► LiF:Mg, Cu, P phosphor in crystal form has been prepared using EFG technique. ► TL intensity increases with increasing annealing temperature from 220 °C to 500 °C ► Highest TL intensity is observed at annealing temperature of 500 °C ► Advantage of EFG technique for developing TL phosphor is discussed.