The build-up of the laboratory-generated dose-response curve and underestimation of equivalent dose for quartz OSL in the high dose region: A critical modelling study

The application of a regeneration procedure for optically stimulated luminescence (OSL) dating requires that the dose-response curve (DRC) of a natural sample is the same as that of a laboratory-generated one. However, the build-up of the laboratory-generated DRCs of quartz has been widely reported in the literature, i.e., the laboratory-generated DRCs are significantly higher than the natural counterparts in the high dose region (above 150 or 200 Gy). This results in severe underestimation of equivalent dose (D_e) for quartz OSL in the high dose region during the application of a single-aliquot regenerative-dose (SAR) protocol. However, the potential mechanism governing the build-up of the laboratory-generated DRC is still unclear. In this study, we performed a comprehensive investigation of the natural and laboratory-generated OSL signals and DRCs using a kinetic model for quartz. We compared the differences in charge concentrations between natural and laboratory-irradiated aliquots following irradiation and monitored the competition for holes and electrons during preheat and stimulation, for the natural, regenerative, and test dose cycles. In the course of the modelling, we could see the build-up of laboratory-generated DRCs, the underestimation of D_e, and a double exponential saturation characteristic of the DRCs. We demonstrated a discrepancy in competition for electrons in the deep electron trap and recombination centres during stimulation between the natural, regenerative, and test dose cycles. The simulation results are directly relevant to quartz OSL D_e determination using the SAR protocol and reveal the mechanisms responsible for the experimentally observed different behaviours between natural and laboratory-generated DRCs.