Assessing dose rate effects in TL and OSL dosimeters: A critical look into dose rate models

This work investigates theoretically possible dose rate effects in thermoluminescence (TL) and optically stimulated luminescence (OSL) materials by solving the rate equations for the stimulated luminescence process. Starting with the solution of the One-Trap–One-Recombination-Center (OTOR) model with parameters from the literature, we first showed that this model, with the chosen parameters, does not reproduce real luminescent material properties (e.g., TL curve and dose response). We then studied the physical phenomena responsible for dose rate effects in this model, and the influence of the model parameters on the dose rate response. As a result, we found that charge accumulation in the delocalized bands over unrealistic long periods (¿ hundreds of seconds) is responsible for dose rate effects. Such effect is caused by the particular choice of model parameters. When model parameters based on physical considerations and experimental results are chosen, no dose rate effects are observed. This work provides a deeper understanding of the luminescence process, by identifying the mechanisms that could be responsible for dose rate effects, and a theoretical foundation to the use of luminescent detectors for ultra-high dose rate dosimetry. • Dose rate effects in luminescence materials are investigated theoretically by rate-equation models. • Charge accumulation in the delocalized bands was identified as the mechanism responsible for dose rate effects. • When experimentally-based models are used, the absence of charge accumulation yields a dose-rate independent response.