Effect of Plastic Deformation on the Thermoluminescence ofγ-Irradiated KCl Crystals

The effect of plastic deformation on the thermoluminescence of nominally pure Harshaw KCl samples $\gamma$ irradiated at room temperature has been studied up to 450 °C. In samples plastically strained prior to irradiation a new glow peak appears. It has been found that this glow peak does not follow either first- or second-order kinetics. It is shown that the phosphorescence decay curves of the glow peak are the superposition of five exponential processes. The activation energies and the preexponential factors of these decays are given. Besides this glow peak, in samples strained after irradiation a glow peak at higher temperatures has been observed. It follows second-order kinetics. The study of thermal annealing of the $F$ centers while the temperature of the sample is linearly increased shows that there is an annealing step corresponding to each strain-induced glow peak. These results are discussed in terms of a recently proposed model to explain the thermoluminescence of as-cleaved $\gamma$-irradiated samples. In this model the $F$ center behaves as a recombination center for the interstitial atoms thermally released from traps. At some stage in this process an electron-hole recombination takes place and light is emitted. The relation of these results to the well-known enhancement of the $F$ colorability by ionizing radiation and also to the enhanced thermal stability of the $F$ centers in plastically deformed samples is discussed.