Preprints
https://doi.org/10.5194/gchron-2020-36
https://doi.org/10.5194/gchron-2020-36

  25 Nov 2020

25 Nov 2020

Review status: a revised version of this preprint is currently under review for the journal GChron.

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

Barbara Mauz1, Loïc Martin2, Michael Discher1, Chantal Tribolo2, Sebastian Kreutzer3,2, Chiara Bahl1, Andreas Lang1, and Nobert Mercier2 Barbara Mauz et al.
  • 1Department of Geography and Geology, University of Salzburg, 5020 Salzburg, Austria
  • 2IRAMAT-CRP2A, UMR 5060, CNRS-Université Bordeaux Montaigne, 33600 Pessac, France
  • 3Geography & Earth Sciences, Aberystwyth University, Aberystwyth SY23 3FL, United Kingdom

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 an additionally complicating parameter which is aliquot size 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. This enhancement is most variable for 50–100 μm grains mounted as aliquots of < 8 mm size and is possibly slightly reversed when large grains are mounted as small aliquots owing to the change of the geometrical function. 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 encompass small, medium, large and very large grain sizes measured with small, medium and large aliquots and that each subsample should obtain several gamma doses. In this way the calibration value is obtained from the inverse slope of the fitted line, not from a single data point for all possible irradiation geometries of an individual beta source.

Barbara Mauz et al.

 
Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

Barbara Mauz et al.

Barbara Mauz et al.

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Short summary
Luminescence dating requires irradiating the sample in the laboratory. Some concerns have been published recently about the reliability of the calibration procedure. Here we have addressed these concerns. We found that the interplay between geometrical parameters such as grain size and aliquot size impact on the calibration more than previously thought. The results allow us recommending improved calibration procedure to enhance the reliability of the calibration value.