Mechanism of nonlinearity in the response characteristics of thermoluminescent dosimeters

A new model is proposed for explaining the nonlinearity in the response characteristics of three common thermoluminescent phosphors (CaSO 4 :Dy, CaF 2 :Dy and Mg 2 SiO 4 :Tb). The increased trapping of charge carriers in the dosimetry traps during irradiation, due to a reduction in trapping efficiency of deep traps caused by radiation damage, was found responsible for the supralinearity in TL response of dosimetry peaks and sublinearity in TL response of high temperature peaks of these phosphors at high gamma ray doses. The dose versus TL response characteristics of deep traps in CaSO 4 :Dy was found to vary drastically from batch to batch, and in CaSO 4 :Dy, the sensitisation observed after a gamma ray dose of 10 3 Gy and annealing at 400 degrees C was found useful in low dose measurements.