Preprints
https://doi.org/10.5194/gchron-2021-17
https://doi.org/10.5194/gchron-2021-17

  02 Jun 2021

02 Jun 2021

Review status: this preprint is currently under review for the journal GChron.

Attenuation of beta radiation in granular matrices: implications for trapped-charge dating

Alastair Charles Cunningham1, Jan-Pieter Buylaert1, and Andrew Sean Murray2 Alastair Charles Cunningham et al.
  • 1Department of Physics, Technical University of Denmark, Risø Campus, Roskilde, Denmark
  • 2Department of Geoscience, Aarhus University, Risø Campus, Roskilde, Denmark

Abstract. Mineral grains within sediment or rock absorb a radiation dose from the decay of radionuclides in the host matrix. For the beta dose component, the estimated dose rate must be adjusted for the attenuation of beta particles within the mineral grains. Standard calculations, originally designed for thermoluminescence dating of pottery, assume that the grain is embedded in a homogenous medium. However, most current applications of trapped-charge dating concern sand- or silt-sized dosimeters embedded in granular sediment. In such cases, the radionuclide sources are not homogeneous, but are localized in discrete grains or held on grain surfaces. We show here that the mean dose rate to dosimeter grains in a granular matrix is dependent on the grain-size distributions of the source grains, and of the bulk sediment, as well as on the grain size of the dosimeters. We further argue that U and Th sources are likely to be held primarily on grain surfaces, which causes the dose rate to dosimeter grains to be significantly higher than for sources distributed uniformly throughout grains. For a typical well-sorted medium sand, the beta dose rates derived from surface U and Th sources are higher by 9 % and 14 %, respectively, compared to a homogenous distribution of sources. We account for these effects using an expanded model of beta attenuation, and validate the model against Monte Carlo radiation transport simulations within a geometry of packed spheres.

Alastair Charles Cunningham et al.

Status: open (until 14 Jul 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gchron-2021-17', Guillaume Guérin, 17 Jun 2021 reply
  • RC2: 'Comment on gchron-2021-17', Svenja Riedesel, 22 Jun 2021 reply

Alastair Charles Cunningham et al.

Alastair Charles Cunningham et al.

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Short summary
Mineral grains within sediment or rock absorb a radiation dose from the decay of radionuclides in the host matrix. For the beta dose component, the estimated dose rate must be adjusted for the attenuation of beta particles within the mineral grains. We show here that the mean dose rate to dosimeter grains in a granular matrix is dependent on the grain-size distributions of the source grains, and of the bulk sediment, as well as on the grain size of the dosimeters.