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Environmental dose rate determination using a passive dosimeter: Techniques and workflow for α-Al2O3:C chips

Kreutzer S., Martin L., Guérin G., Tribolo Ch., Selva P., Mercier N.

Geochronometria

2018

Vol. 45, no. 1

56--67

In situ dosimetry (active, passive dosimeters) provides high accuracy by determining environmental dose rates directly in the field. Passive dosimeters, such as α-Al2O3:C, are of particular interest for sites with desired minimum disturbance (e.g., archaeological sites). Here, we present a comprehensive approach obtaining the environmental cosmic and γ-dose rate using α-Al2O3:C chips. Our procedure consists of (1) homemade field containers, (2) a homemade bleaching box, (3) a rapid measurement sequence and (4) software based on R to process the measurement results. Our validation steps include reproducibility, irradiation time correction, cross-talk evaluation and source calibration. We further simulate the effect of the container against the infinite matrix dose rate, resulting in attenuation of ca. 6%. Our measurement design uses a lexsyg SMART luminescence reader equipped with green LEDs. The irradiation is carried out under the closed β-source. The minimum dose that can be determined was estimated with ca. 10 μGy. However, we also show that for the equipment used, an irradiation time correction of ca. 2.6 s is needed and irradiation cross-talk should be taken into account. The suggested procedure is cross-checked with four reference sites at Clermont-Ferrand showing a good γ-dose rate for three out of the four sites. Finally, an application example, including needed analytical steps, is presented for dosimeters buried at the archaeological site of the Sierra de Atapuerca (Spain).

Field gamma spectrometry, Monte Carlo simulations and potential of non-invasive measurements

Guérin G., Mercier N.

Geochronometria

2012

Vol. 39, no. 1

40-47

The determination of gamma dose rates is of prior importance in the field of luminescence dating methods. In situ measurements are usually performed by the insertion of dosimeters or a porta-ble gamma spectrometer cell in sediments. In this paper, Monte-Carlo simulations using the GEANT4 toolkit allow the development of a new technique of in-situ gamma dose rate evaluations: a spectrom-eter cell is placed on the surface of sediments under excavation to acquire successive spectra as sedi-ments are removed by excavations. The principle of this non-invasive technique is outlined and its po-tential is discussed, especially in the case of environments in which radioelements are heterogeneous-ly distributed. For such cases, a simple method to reconstruct gamma dose rate values with surface measurements using an attenuator is discussed, and an estimation of errors is given for two simple cases. This technique appears to be applicable, but still needs experimental validation.