基于EMCCD成像系统的释光测量技术——基本流程与参数设置

Accurate and efficient recording of luminescence signals is a vital foundation for optically stimulated luminescence (OSL) dating. The conventional OSL technique uses photomultiplier tube (PMT) to detect the luminescence signals arising from minerals, which can obtain one-dimensional information on the variation of luminescence signals with time. The luminescence imaging method based on an electron multiplying charge-coupled device (EMCCD) further records the spatial variation of those signals, making OSL dates spatially resolved, such as luminescence measurements of single-grain and slice, enable the analysis of sediment dating, rock surface luminescence dating, and thermoluminescence dating to be more accurate and reliable. In this study, we introduced an EMCCD imaging system equipped on a Risø TL/OSL reader. Using dose recovery tests of single-grain quartz and K-feldspar samples under different EMCCD settings, we focus on the influences of parameters on the luminescence image and data quality, which are aperture, wavelength, height, channel and region of interest (ROI). A brief flow of applying the EMCCD imaging system for OSL dating was then summarized. Our results show that: 1) Larger aperture (10~20 mm) and ROI (Risø standard single-grain disc, φ=450 μm) help to enhance luminescence intensity and improve the reliability of effective OSL data, while the definition of ROI should be balanced between the luminescence intensity and the crosstalk; 2) Wavelength and height parameters, probably independent of measured luminescence intensity and data quality, are beneficial to obtaining clearer images; 3) The setting of channels is suggested to be adapted to the luminescence decay characteristics of the measured minerals to improve the signal-to-noise ratios; 4) Hotspots inevitably existed in the EMCCD images have a negligible effect on the equivalent dose measurement. This study will provide a reference for improving the accuracy and precision in obtaining EMCCD OSL data and promoting its application in the future.