Dose evaluation using multiple-aliquot quartz OSL: test of methods and a new protocol for improved accuracy and precision

Abstract

Multiple-aliquot quartz OSL dose-response curves often suffer from substantial variability in the luminescence output from identically treated aliquots (scatter) that leads to large uncertainties in the equivalent-dose estimates. In this study, normalisation and its bearing on the accuracy and precision of the equivalent-dose estimates is investigated. We conclude that the most commonly used procedure employing the natural OSL (natural normalisation), leads to both poor accuracy and poor precision in the equivalent-dose estimates as it is insensitive to possible dose-dependent and non-dose-dependent sensitivity changes during the pre-heat, and fundamental variability in the shapes of quartz OSL (blue-green or blue-light stimulated luminescence) decay forms. A new protocol using a combination of 'elevated temperature IR cleaning' (ETIR) and 'component-specific dose normalisation' (CSDN) has been developed. CSDN accounts for variability in the OSL decay forms and absorbs such sensitivity changes. A combination of ETIR and CSDN protocol increased palaeodose precision from ±100% to ±4% in quartz separates from the fluvially transported sands in the Thar desert. A comparison with palaeodose estimates from the single-aliquot-regeneration protocol (SAR) gave similar accuracy and precision.