Effect of dopants on TL characteristics of LiF:Mg,Cu,P detectors
Abstract LiF:Mg,Cu,P detectors produced at the Institute of Nuclear Physics in Krakow have shown very good dosimetric characteristics. Understanding of the effect of the concentration and type of dopants is important in the characterization of TL materials. The aim of work was to investigate the influence of the type and concentration of the dopants on the photon energy response of these detectors by irradiations “in air” and on the ISO water phantom in the range of mean photon energies between 33 and 164 keV. The influence of dopants on the glow curves, sensitivity and reproducibility was also examined. Results showed that measured energy dependence values are lower compared to the theoretical values both “in air” and on phantom. The type and concentration of the dopants influence the shape of the glow curves and sensitivity while for energy dependence is more important the presence of certain activators, namely copper.
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.
Measurements of emission spectra during thermoluminescence (TL) from LiF(Mg, Cu, P) TL dosimeters
A detailed analysis of the spectrum of the light emitted during thermoluminescence (TL) from irradiated LiF(Mg, Cu, P) is presented. The data show how the emission characteristics vary as functions of the concentrations of the individual dopants (Mg, Cu and P) and of the pre-irradiation heat treatments. It is suggested that the data can be interpreted in terms of precipitated phases of Mg and P. It is speculated that the heat treatments cause the dissolution of these phases and this in turn alters the glow-curve structure and leads to a reduction of the TL sensitivity.