Effects of various storage times and photon energies on the kinetic parameters of glow curves of CaF 2:Tm (TLD-300)

Abstract

In the present paper, fading and radiation quality effects on the kinetic parametes of dosimetric peaks were investigated. A nonlinear least-squares numerical fitting program based on the Levenberg-Marquardt algorithm was developed to analyze the glow curves. General-order kinetics formula with a single energy level of traps was adopted as the fitting function. The results indicate that both fading and photon energies have pronounced influence on the kinetic parameters. In the storage times experiments, change in traps distribution due to diffusion at room temperature may be the main reason causing the variations in activation energies. In the different sources experiments, different spatial distributions of trapped charge carries due to the different photoelectric effect of different photon energies may influence the binding energies. Other factors such as trapped charge conversion from one type of trap to another, competing non-radiation defect interaction and different photon energies may be used for interpreting the drift phenomenon of activation energies. Temperature dependence of frequency factor, variations of temperature lag and fluctuation and shift of the distribution frequency factor can be used to interpret the drift phenomenon of frequency factor. Kinetic order variation during the heating stage can also be used to interpret the drift phenomenon of kinetic order. Peak 3 of 55Fe (high LET radiation) irradiated samples exhibits a different character with respect to peak 3 of other source-related glow curves. This may be due to the invalidity of the general-order equation and the increase of retrapping probability.