Cross-Calibration of an α-Source Used for Luminescence Dating by Applying Different Samples and Procedures

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Version: Final published version
License: CC BY-NC-ND 4.0
Serval ID
serval:BIB_CD50AB4231AF
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Cross-Calibration of an α-Source Used for Luminescence Dating by Applying Different Samples and Procedures
Journal
Geochronometria
Author(s)
Sipos György, Schmidt Christoph, Bartyik Tamás, Filyó Dávid, Magyar Gergő, Havasi Viktor, Kukovecz Ákos
ISSN
1897-1695
Publication state
Published
Issued date
01/01/2021
Volume
48
Number
1
Pages
61-72
Language
english
Abstract
In terms of fine-grain luminescence dating applications, the efficiency of a-radiation in producing luminescence is an important issue when determining environmental dose rates. Efficiency is usually assessed by measuring the ratio of luminescence intensities induced by known a and b laboratory doses. Consequently, most thermoluminescence (TL)/optically stimulated luminescence (OSL) readers besides the standard 90Sr/90Y b-source can also be equipped with a 241Am a-source. A crucial point is, however, the calibration of these sources. The calibration of b-sources is routinely performed using standard quartz samples previously irradiated by a known g-dose, though, in the case of a-sources, the procedure is less standardised, partly because there are no calibration materials with a known a-efficiency value.
In this study, we aimed to cross-calibrate the built-in a-source of a RISØ TL/OSL DA-20 luminescence reader by testing and comparing five procedures, applying different samples (quartz and polymineral), different protocols multiple aliquot regeneration (MAR) and single aliquot regeneration (SAR) and different calibration sources. Throughout the tests, the performance of the fine-grain RISØ calibration quartz was also assessed.
Regardless of the applied procedure, the calculated a-dose rates with one exception gave similar results. On the one hand, the applied polymineral sample due to potential fading, fairly high residuals after bleaching and relatively low infrared stimulated luminescence (IRSL) sensitivity proved to be the least optimal choice for cross-calibration. On the other hand, the tested natural fine grain quartz gave almost identical results when using different types of bleaching and different calibration a-sources. The mean dose rate determined for the source was 0.080 ± 0.004 Gy/s.
The cross-calibration by using the RISØ fine grain quartz yielded somewhat higher but at the apparent uncertainty of luminescence dating still not significantly different dose rate for the source under calibration. Tests showed that the calibration quartz saturates at a relatively low a-dose, and the shape of a- and b-dose-response curves also depart from each other quite early, suggesting that cross-calibration with this material seems to be reliable only at low doses. For the first time, the a-value of the fine-grain calibration quartz was also determined using the freshly calibrated a-source, and the measurement yielded a 0.054 ± 0.003 value. We propose that after further validation of this result, the RISØ calibration quartz can ease the dose rate assessment of uncalibrated a-sources in the future.
Keywords
Earth and Planetary Sciences (miscellaneous)
Web of science
Open Access
Yes
Create date
03/01/2022 14:13
Last modification date
07/01/2022 8:12
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