DOI: 10.4121/31c191c4-3fce-45cb-8fda-5597c1038e52.v1
title: Data underlying the publication: A novel method to assess crosstalk in single-grain luminescence detection

description: For more information please see the README file in the "Data-4TU" folder which contains all scripts, data, and a manual.<br># Paper abstract <br> Luminescence imaging with an EMCCD camera is an innovative approach to single-grain luminescence detection. In theory, it allows for the random placement of grains on a disc, but in practice, attributing photons to specific grains remains unachievable. Currently, single-grain discs with fixed grain placement are primarily used, though these are still susceptible to crosstalk, e.g. overlapping of luminescence signals from adjacent grains. A standardized method for identifying, correcting, or eliminating crosstalk is not yet available. In this paper, we introduce Moran’s I, a measure of spatial autocorrelation, as a novel method for assessing crosstalk in single-grain luminescence detection. Using simulations with induced crosstalk, we demonstrate that Moran’s I can effectively detect crosstalk when interpreted within the context of its pseudo-p value. These results are corroborated by those obtained on a measured luminescence dataset for which crosstalk is deliberately enhanced by increasing the region of interest (ROI) selected for luminescence signal integration. These results on simulated and measured data show that Moran’s I can be used to select optimal ROI size to enhance signals whilst limiting crosstalk. Finally, we examined the effect of modelled crosstalk on three types of equivalent-dose distributions, finding that normal distributions are unaffected by crosstalk, whereas bimodal distributions became mixed, and the shape of skewed distributions alters. These results have implications for ROI selection for well-bleached, mixed and heterogeneously bleached sediments. <br># Measurements <br>+ Luminescence measurementsAll measurements were made on a Risø TL/ OSL DA-20 reader with an automated detection and stimulation head (DASH) and an EMCCD camera (Kook et al., 2015). The system is fitted with a calibrated 90Sr/90Y beta source which delivers a dose rate of approximately 0.0954 Gy/s to grains on a single-grain disc. The sample was stimulated with IR LEDs at 850 nm and a blue package filter (BG-3 (3.0 mm) + BG-39 (4.0 mm)) was used to target the 410 nm K-feldspar emission peak. We adopted a multi-elevated-temperature (MET) pIRIR measurement protocol with IRSL read-outs at 50, 110, 170, and 230 ◦C (Table 1) (Li & Li, 2011). We measured three single-grain discs per sample, which makes a total of 45 discs. We chose to only study crosstalk effects on the IRSL-50 signal for the net natural test dose (8.1 Gy) response (Table 1, step 12 manuscript), which carries information about the luminescence sensitivity of the grains. The net natural test dose response (Net_TnTx ± Net_TnTx.Error) was alculated by subtracting the background test dose response (TnTx.BG) integrated over channel 210 up to 260 (20 s) from the initial test dose response (TnTx) integrated over channel 11 up to 31 (8 s) to create a single-grain brightness distribution (Wallinga, 2002). The measured data were analyzed with Risø Viewer+ software and extracted for nine different ROI sizes: 300, 450, 600, 750, 900, 1050, 1200, 1350 and 1500 μm, i.e. ranging from the hole dimension (300 μm) up to overlapping with the adjacent grain hole (1500 μm). The spacing between grain positions on the single-grain disc is 600 μm. We assume that grains of varying sensitivity are randomly distributed over the single-grain disc grid. Subsequent analyses were performed within the R environment for statistical computing. <br>Please visit the Netherlands Centre for Luminescence dating (NCL) database for more information on the sample background at: https://www.lumid.nl/.  On the website go to the 'projects' tab and search for NCL-code 1321.<br>+ Measurement protocols and data formats The measurement protocols were written in Riso's sequence editor software (.seq files). All Riso software is downloadable at: https://www.fysik.dtu.dk/english/research/radphys/research/radiation-instruments/tl_osl_reader/software. The raw data is stored in a Riso .binx file which can be opened in Riso's analyst software environmen. We analyzed the raw data in Riso's Viewer+ to extract the luminescence signal for several Region Of Interests (ROIs). <br>+ Processing and analysis scripts in R All processing of data (modifications, calculations, etc) and analysis of data was performed in R. All  scripts are commented. Per measurement type an R script was written.  <br>+ Figures and tables All figures and tables were created through R and/ or Adobe Illustrator. Refer to the R scripts for detailed information within the script.