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 me asurement cycle, consisting of a 10 s preheat at a given temperature f ollowed by a 0.1 s exposure to green light at 110 degrees C, can be we ll represented by exponential decay. The decay constant of about 8% pe r cycle is insensitive to preheat temperatures below about 250 degrees C, but increases to about 35% per cycle at 280 degrees C. This increa se is attributed to increasing thermal erosion of the main OSL trap. T he decay constant is also shown to be insensitive to dose. An additive -dose protocol is presented which requires only one aliquot for the es timation of the equivalent dose (D-e). This protocol has been applied to quartz from 11 Australian sites. To illustrate the value of the sin gle-aliquot approach, the apparent values of D-e for 14 samples, conta ining doses of between 0.01 and 100 Gy, have been measured in triplica te at preheat temperatures of between 150 and 300 degrees C, using a s ingle aliquot for each D, measurement. It is shown that low temperatur e preheats (similar to 200 degrees C for 10 s) are appropriate for the younger samples containing the smaller doses, but a much higher tempe rature preheat (greater than or equal to 280 degrees C for 10 s) is re quired for the older samples containing the larger doses. Excellent ag reement is found between these single-aliquot estimates of D-e and tho se from additive-dose multiple-aliquot protocols. over the entire dose range. (C) 1997 Elsevier Science Ltd.