Equivalent dose determination using a quartz isothermal TL signal

We report on further developments in the use of an isothermal thermoluminescence (ITL) signal for determining the equivalent dose (D(e)) in unheated sedimentary quartz. In order to minimise sensitivity change during the first measurement, the ITL signal is measured at 270 degrees C following a preheat at 300 degrees C for 10 s. The decay curve can be represented well by the sum of two exponentially decaying functions plus a constant. The two decaying components hold the dosimetric information; they both appear to originate with the 325 degrees C region of the glow curve, and are thermally stable. This composite signal can be fully reset by sunlight, and grows with dose over at least the same range as the OR signal. A single-aliquot regenerative-dose (SAR) protocol can be used with this ITL signal. Dose recovery experiments confirm the suitability of the measurement protocol; the D(e) values are in acceptable agreement with the expected burial dose in samples from a variety of depositional environments and ages. Our results suggest that measurement of the ITL signal at 270 degrees C enables the quartz 325 degrees C TL peak to be used for accurate dose measurements on a single aliquot. The signal allows dating over at least the same age range as the OSL signal, and it appears especially advantageous for application to quartz samples for which the OR signal saturates below similar to 500 Gy. (C) 2009 Elsevier Ltd. All rights reserved.