Discrimination of LINAC photon and sunlight contributions in watch glass analyzed by means of thermoluminescence

The research described in this paper shows how to extract from the glow curves of watch glasses exposed to LINAC photons and sunlight a contribution sensitive to LINAC photons dose. As first step, the dependence of the TL signal due to sunlight on the exposure duration was studied and a signal saturation was observed after about 20 weeks. The comparison of TL signals due to solar light and to LINAC photons highlights a partial overlap of the two signals. Here, two different analysis procedures of glow curves (general order kinetics deconvolution and principal components analysis) are reported to point out components which depend differently on LINAC photon radiation dose. For both analyses two components were used and the dependence on dose was investigated. In order to evaluate the ability of both techniques to reconstruct absorbed doses a blind test was performed. The reconstructed dose with both techniques is significantly consistent with the initial dose value. The procedures here described are valuable because they could be used to discriminate any background signal from that due to ionizing radiation irradiation and could be used as useful tools for dose reconstruction in retrospective dosimetry.