Cross-talk during single grain optically stimulated luminescence measurements of quartz and feldspar

Focussed laser systems designed to measure the optically stimulated luminescence (OSL) signals from individual sand sized mineral grains are now widely used. One system that is commonly used can hold up to 100 grains on a 9.8 mm diameter aluminium disc, and can use either a green or infrared (IR) laser for optical stimulation. The grains are held in holes drilled into the disc surface, and the spacing between the edges of adjacent holes is only 300 μm. Focussing of the laser is essential to prevent inadvertent optical stimulation of adjacent grains, but no measurements have previously been made to determine the extent of cross-talk. Measurements on two systems show that the maximum cross-talk for an adjacent position is 0.22%, but typically the value is 0.04% for the green laser and 0.08% for the IR laser. This magnitude of cross-talk is unlikely to have a significant impact on continuous wave OSL measurements where the period of optical stimulation tends to be short, but may be important in linearly modulated OSL measurements where long periods of stimulation are sometimes used to characterise slow components of the OSL signal.

► Measure the cross-illumination that occurs in single grain OSL measurements. ► Largest value 0.22%, but more typically 0.04–0.08% on adjacent positions. ► Most likely to have an impact during long stimulations used for LM-OSL.