Investigations into the reliability of SAR-OSL equivalent doses obtained for quartz samples displaying dose response curves with more than one component

Fast component dominated quartz single aliquot regenerative dose optically stimulated luminescence (SAR-OSL) dose response curves that display continuing growth at high doses are increasingly reported in literature. This behaviour would result in higher equivalent doses being obtained. Here we document the characteristics of OSL signals from fine (4–11 μm) and coarse (63–90 μm) quartz extracted from Romanian loess that display such behaviour. For very high doses (>1 kGy up to 5–15 kGy) the data could be closely fitted to a double saturating exponential regression model. Nonetheless, the saturation charcteristics of these fine and coarse quartz grains are very different, with average saturation chracteristic doses of D01 ≈ 175 Gy and D02 ≈ 1800 Gy in the case of the fine material, while in the case of the coarse material values of D01 ≈ 55 Gy and D02 ≈ 600 Gy have been obtained. Our results imply a hitherto unexplained mechanism in OSL production at high doses and question the reliability of obtaining SAR-OSL equivalent doses in the high dose region when a second function is needed to describe the dose response.

► We document dose response of SAR OSL signals of fine and coarse sedimentary quartz.
► For high doses (>1 kGy) data was fitted to a double saturating exponential model.
► The saturation characteristics of fine and coarse quartz grains are very different.
► The natural signal of an infinitely old sample was found not to be in saturation.
► We question the reliability of obtaining equivalent doses in the high dose region.