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Calibrating gamma dose rates for palaeodosimetric dating systems: Evaluating dose rate gradients

, , , , , and . UK meeting on luminescence and ESR dating, University of Liverpool, Liverpool, (11th-13th July 2016)

Abstract

In palaeodosimetric dating systems, such as luminescence and electron spin resonance dating, the cumulative effects of exposure to ionising radiation in natural materials, quantified as equivalent doses, and related to dose rates in order to determine ages. The dose rates applicable are due to alpha, beta and gamma radiation of natural decay series radionuclides, beta and gamma contributions of natural potassium and rubidium, and an additional contribution from cosmic radiation. While alpha and beta dose rate contributions originate within dating samples, gamma and cosmic contributions come from the surrounding environment and are estimated using a combination of in-situ measurements and modelling. In-situ gamma spectrometry and in-situ luminescence dosimetry are two approaches which can be used to determine dose rates in the complex stratigraphy of archaeological or environmental sites. These approaches are usually calibrated relative to reference fields of homogeneous materials with known concentrations of naturally occurring radionuclides. This poster describes work being undertaken at SUERC to characterise two new reference boxes of 1.2m x 1.2m dimension containing known quantities of rock aggregates from two Scottish Quarries. The boxes were constructed ahead of the UKLUM15 meeting in Glasgow, and working values of the dose rates within the boxes were estimated based on laboratory gamma spectrometry of 54 samples taken during filling. Two access tubes are present to facilitate instrumental or dose rate measurements, and initial simulations of the dose rate gradients in the tubes were conducted by Loic Martin using the DOSIVOX tool. These predict an asymmetric dose rate gradient across the box with central areas of constant dose rate. Here we use a combination of in-situ gamma spectrometry and luminescence dosimetry to measure the dose rate gradients within the boxes and compare the outcomes with simulated predictions.

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akintunde2016calibrating
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