A portable luminescence dating instrument

We describe a portable luminescence reader suitable for use in remote localities in the field. The instrument weighs about 8kg and is based around a 30mm bialkali photomultiplier detecting signals through a glass filter centered on 340nm. Stimulation is by 470nm blue LEDs (24W in total) operating in both continuous wave and pulsed mode; photon counting can be gated such that it is active only during the pulse off-period.

There are also two bleaching light sources (470nm, 5W and 940nm, 3W), and the luminescence signals can be regenerated using a cold-cathode 30kV X-ray tube, delivering ∼0.06Gy.s−1. The three position sampling device has a heating element under each sampling position, able to heat the sample at 3°C.s−1 up to at least 250°C.

The sampler can be inserted into unconsolidated sediments, and is designed to prevent exposure of the mineral grains to ambient light during sampling. The performance of the instrument in terms of sensitivity and reproducibility is comparable to that of the standard bench-top laboratory TL/OSL Risø reader.We show that the portable luminescence reader is able to measure accurately an ∼20Gy quartz burial dose in a natural (unpretreated, no mineral separation) sandy sediment.

We also show that, because of the configuration of the measurement head, the portable reader can be used to measure radioluminescence at elevated temperature in the presence of stimulation light; this facility is not available on conventional bench-top instruments. It is concluded that the portable luminescence reader can be used to accurately determine the quartz burial dose in loose sandy sediments in the field, without sample preparation or darkroom facilities.