Technical note: on the reliability of laboratory beta-source calibration for luminescence dating

Mauz, B., Martin, L. , Discher, M., Tribolo, C., Kreutzer, S., Bahl, C., Lang, A. and Mercier, N. (2021) Technical note: on the reliability of laboratory beta-source calibration for luminescence dating. Geochronology, 3(1), pp. 371-381. (doi: 10.5194/gchron-3-371-2021)

Abstract

The dose rate of the 90Sr = 90Y beta source used in most luminescence readers is a laboratory key parameter. There is a well-established body of knowledge about parameters controlling accuracy and precision of the calibration value but some hard-to-explain inconsistencies still exist. Here, we have investigated the impact of grain size, aliquot size and irradiation geometry on the resulting calibration value through experiments and simulations. The resulting data indicate that the dose rate of an individual beta source results from the interplay of a number of parameters, most of which are well established by previous studies. Our study provides evidence for the impact of aliquot size on the absorbed dose in particular for grain sizes of 50–200 μm. For this grain-size fraction, the absorbed dose is enhanced by ~ 10 %–20% as aliquot size decreases due to the radial increase of dose rate towards the centre of the aliquot. The enhancement is most variable for 50–100 μm grains mounted as aliquots of <8mm size. The enhancement is reversed when large grains are mounted as small aliquots due to the edge effect by which the dose induced by backscattered electrons is reduced. While the build-up of charge dictates the increase of absorbed dose with the increase of grain size, this principle becomes more variable with changing irradiation geometry. We conclude that future calibration samples should consist of subsamples composed of small, medium, large and very large quartz grains, each obtaining several gamma doses. The calibration value measured with small, medium and large aliquots is then obtained from the inverse slope of the fitted line, not from a single data point. In this way, all possible irradiation geometries of an individual beta source are covered, and the precision of the calibration is improved.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Martin, Dr Loic
• Authors: Mauz, B., Martin, L., Discher, M., Tribolo, C., Kreutzer, S., Bahl, C., Lang, A., and Mercier, N.
• Subjects: C Auxiliary Sciences of History > CC Archaeology; Q Science > QC Physics; Q Science > QE Geology
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Geochronology
• Publisher: Copernicus Publications
• ISSN: 2628-3719
• ISSN (Online): 2628-3719
• Copyright Holders: Copyright © 2021 The Authors
• First Published: First published in Geochronology 3(1): 371-381
• Publisher Policy: Reproduced under a Creative Commons License