Microdosimetric modeling of the relative efficiency of the optical absorption of LiF:Mg,Ti (TLD-100) detectors exposed to 1H and 4He ions

Abstract The Microdosimetric d(z) Model was used in combination with simulated microdosimetric specific energy probability distributions for monoenergetic 1H and 4He ions (energy range = 0.1–1000 MeV/n, target size range = 1–2000 nm) to investigate the possibility of modeling the relative efficiency of two optical absorption (OA) bands (4.77 and 5.08 eV) in the OA energy spectra of LiF:Mg,Ti (TLD-100) thermoluminescent detectors. This work represents the first application of the model to a physical system other than thermally- and optically-stimulated luminescence. The 4.77 eV OA trap is populated by electrons liberated during irradiation and its experimental OA relative efficiency was successfully predicted using a target size of 9 nm in the simulations. On the other hand, the model was not able to reproduce the values of the experimentally-observed proton induced OA efficiency above unity for the 5.08 eV OA band associated with the F centers in LiF:Mg,Ti (electron occupied Fluoride vacancy). The F centers are initially present in the LiF lattice but are also created by the irradiation. Since the absence of defect creation by the irradiation is a necessary condition of the microdosimetric model, the discrepancy between the model results for the F band and the experimental data was not unexpected. The calculations for both OA bands are presented as a function of the particle energy and the simulated microdosimetric target size and will be useful in further applications of the model OA relative efficiencies for charged particles.