<abstract xmlns="http://www.w3.org/1999/xhtml">

In terms of fine-grain luminescence dating applications, the efficiency of α-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 α and β laboratory doses. Consequently, most thermoluminescence (TL)/optically stimulated luminescence (OSL) readers besides the standard 90Sr/90Y β-source can also be equipped with a 241Am α-source. A crucial point is, however, the calibration of these sources. The calibration of β-sources is routinely performed using standard quartz samples previously irradiated by a known γ-dose, though, in the case of α-sources, the procedure is less standardised, partly because there are no calibration materials with a known α-efficiency value.
In this study, we aimed to cross-calibrate the built-in α-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 α-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 α-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 α-dose, and the shape of α- and β-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 <italic>a</italic>-value of the fine-grain calibration quartz was also determined using the freshly calibrated α-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 α-sources in the future.
</abstract>

In terms of fine-grain luminescence dating applications, the efficiency of α-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 α and β laboratory doses. Consequently, most thermoluminescence (TL)/optically stimulated luminescence (OSL) readers besides the standard 90Sr/90Y β-source can also be equipped with a 241Am α-source. A crucial point is, however, the calibration of these sources. The calibration of β-sources is routinely performed using standard quartz samples previously irradiated by a known γ-dose, though, in the case of α-sources, the procedure is less standardised, partly because there are no calibration materials with a known α-efficiency value.
In this study, we aimed to cross-calibrate the built-in α-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 α-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 α-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 α-dose, and the shape of α- and β-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 α-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 α-sources in the future.

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

Department of Geoinformatics, Physical and Environmental Geography, Geochronological Research Group

Chair of Geomorphology, Faculty of Biology, Chemistry and Earth Sciences

Department of Applied and Environmental Chemistry

Geochronometria

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

In terms of fine-grain luminescence dating applications, the efficiency of α-radiation in producing luminescence is an important issue when determining...

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

Article Category: Conference Proceedings of the 13th International Conference “Methods of Absolute Chronology” June 5–7th, 2019, Tarnowskie Gory, Poland

Publicado en línea: 29 jun 2021

Páginas: 61 - 72

Recibido: 30 may 2020

Aceptado: 12 feb 2021

DOI: https://doi.org/10.2478/geochr-2021-0003

Palabras clave
luminescence dating, a-source, cross-calibration, a-value, fine-grain RISØ calibration quartz

© 2021 György Sipos et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

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

Article Category: Conference Proceedings of the 13th International Conference “Methods of Absolute Chronology” June 5–7th, 2019, Tarnowskie Gory, Poland

Publicado en línea: 29 jun 2021

Páginas: 61 - 72

Recibido: 30 may 2020

Aceptado: 12 feb 2021

DOI: https://doi.org/10.2478/geochr-2021-0003

Palabras claveluminescence dating, a-source, cross-calibration, a-value, fine-grain RISØ calibration quartz

© 2021 György Sipos et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Palabras clave
luminescence dating, a-source, cross-calibration, a-value, fine-grain RISØ calibration quartz