In Situ Dose Rate Determination: First Measurements by the Use of BeO OSL Dosimeters within the Purpose of Luminescence Dating

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Franz Hartung is PhD student and research associate at the Cologne Luminescence Laboratory and the project F2 of the CRC 806 “Our way to Europe” and investigates dose rate determination techniques within the context of trapped charge dating methods. Before he came to Cologne, Franz Hartung studied Physics at the TU Dresden and graduated with a diploma degree, whereas the thesis was written in the radiation Physics group (ASP) in the institute of nuclear and particle Physics (IKTP).

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Franz Hartung, Project F2

The determination of the environmental dose rate is an essential part of trapped charge dating techniques, which especially becomes apparent in the age equation t = De / Ḋ, where the age t is calculated by the quotient of the equivalent dose De and the environmental dose rate  [1].
One opportunity to determine is the approach of in situ dosimetry. The most important benefit of this approach is to perform measurements in the original occurring radiation field. Thus the effect of uninfluenced environmental conditions, like heterogeneous sediments, the cosmic radiation and a varying water content can be recorded directly.
A device that enables to determine the part of the dose rate , that is caused by cosmic and γ-radiation, and that applies in situ measurements is the BeOmax dosimetry system (see Figure above) [2]. Originally developed for the purpose of personal dosimetry, the BeOmax dosimetry system is also useable for further scientific applications. The system consists of small OSL dosimeters with beryllium oxide (BeO) as luminophore and of special designed reader and bleaching units, which makes it easy to handle. It is calibrated to dose in air.
This study is one of the first to test and show the properties of the BeOmax dosimetry system in terms of luminescence dating. The dose rates is of the in situ measurements at different sites and setups were compared to the dose rates sp that were ascertained in laboratory γ-spectrometric measurements. The in situ measurements resulted in sufficient sensitivity to reveal heterogeneities of dose rate influencing parameters. However, the comparison to corresponding γ-spectrometric measurements pointed out, that the absolute values of the in situ measurements are not yet usable for dating. The comparison also showed is > sp at one of the sites and is < Ḋsp at a different site. Whether or not this behaviour can be explained by a possible correlation between the spectrometric determined element concentrations and is , has to be confirmed. For that purpose radiation transport simulating codes will be used.

References:
[1] M. J. Aitken: An Introduction to Optical Dating, Oxford University Press, Oxford, 1998
[2] A. Jahn, M. Sommer, W. Ullrich, M. Wickert, J. Henniger, Radiation Measurements 56 (2013), 324-327

Event Information:

Date, Time: 01/02/2016, 14:45 h – 15:30 h

Location: Room S22, Seminargebäude (Building 106), Universitätsstraße 37 , Cologne

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