首页|Beta dose heterogeneity in sediment samples measured using a Timepix pixelated detector and its implications for optical dating of individual mineral grains
Beta dose heterogeneity in sediment samples measured using a Timepix pixelated detector and its implications for optical dating of individual mineral grains
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NSTL
Elsevier
Single-grain optical dating has been widely used to estimate depositional ages for Quaternary sediments. An understanding of the sources influencing the dispersion of equivalent dose (D-e) estimates from individual grain measurements is essential for accurate age determination. Beta microdosimetry (i.e., beta dose deposition at the sub-millimetre scale) is a known cause of spread in single-grain D-e values, so the detection and assessment of beta dose rate (D-beta) variation is important to properly interpret these data. Here we demonstrate the application of Timepix, a pixelated detector that directly measures in situ beta emissions based on cluster analysis, to determine the beta microdosimetry of natural sediment samples from a cave deposit in Russia and a sand dune in Australia. We describe a Timepix measurement and data processing procedure for natural sediments, and establish sample specific calibration curves using associated sample radioelement concentrations to convert Timepix count rates into estimates of D-beta. On the basis of the Timepix analysis, a 2D 'heat map' of D-beta at sub-millimetre resolution was obtained for each sample. Our results show that the D(beta )estimates are heterogeneous and their non-uniformity gives rise to 9 & nbsp;+/- 4 to 26 & nbsp;+/- 5%& nbsp; overdispersion in the single-grain D-e distributions for the samples examined here. We discuss the likely sources of D-beta heterogeneity, based on micromorphological investigations of these sediment samples, which include a variety of materials present in natural deposits associated with D-beta 'hot' and 'cold' spots. A comparison of the D-beta dispersion with that of the corresponding single-grain D-e values shows that the scatter among the latter can be fully or partly explained by beta microdosimetry and other known sources of overdispersion.
NSTL
Elsevier
