Equivalent dose measurement using a single aliquot of quartz

The principles behind an additive-dose single-aliquot protocol and the need for such a protocol are outlined. It is shown for two Australian sedimentary quartz samples that the decay of OSL during a repeated measurement cycle, consisting of a 10 s preheat at a given temperature followed by a 0.1 s exposure to green light at 110 degrees C, can be well represented by exponential decay. The decay constant of about 8% per cycle is insensitive to preheat temperatures below about 250 degrees C, but increases to about 35% per cycle at 280 degrees C. This increase is attributed to increasing thermal erosion of the main OSL trap. The decay constant is also shown to be insensitive to dose. An additive-dose protocol is presented which requires only one aliquot for the estimation of the equivalent dose (D-e). This protocol has been applied to quartz from 11 Australian sites. To illustrate the value of the single-aliquot approach, the apparent values of D-e for 14 samples, containing doses of between 0.01 and 100 Gy, have been measured in triplicate at preheat temperatures of between 150 and 300 degrees C, using a single aliquot for each D, measurement. It is shown that low temperature preheats (similar to 200 degrees C for 10 s) are appropriate for the younger samples containing the smaller doses, but a much higher temperature preheat (greater than or equal to 280 degrees C for 10 s) is required for the older samples containing the larger doses. Excellent agreement is found between these single-aliquot estimates of D-e and those from additive-dose multiple-aliquot protocols. over the entire dose range. (C) 1997 Elsevier Science Ltd.