Evaluation of SAR procedures for De determination using single aliquots of quartz from two archaeological sites in South Africa

In previous work the conventional SAR procedure has been demonstrated to work well for a large number of samples. Application of the conventional SAR procedure (but with a range of preheat temperatures) to naturally irradiated quartz grains from two different archaeological sites in South Africa showed substantial changes in sensitivity through the measurement cycles; one sample (SIB2) showed no trend in De as a function of preheat temperature, showing that the sensitivity correction was appropriate, whereas for the other sample (ZB4) there was a trend that could be related to the growth curve construction, rather than measurement of the natural signal. However, application of a conventional SAR procedure, with a 260 °C preheat for 10 s and a cut heat at 160 °C, to quartz grains that had been bleached and given a laboratory dose, resulted in underestimation of the dose by ⩾10%. The effect of raising the cutheat temperature from 160 °C was investigated using LM-OSL measurements in order to identify OSL components that are present in addition to the fast component for which SAR was developed. The effects of changing the cutheat temperature and adding a high-temperature optical stimulation between cycles in the SAR procedure were measured for dose recovery tests. The effects of these changes on measurement of De values for single aliquots of these two samples are reported. Both modifications improved De recovery, and the study emphasizes the importance of carrying out dose recovery tests