Abstract
<p class="Abstract"><span lang="EN-GB">In authenticity tests using the thermoluminescence (TL) method, the sampling phase is fundamental to collecting an appropriate amount of powder for analysis. The powder is usually obtained by drilling in hidden and pertinently selected areas of an artefact. During the drilling, a local temperature increase can occur, and, because thermoluminescence emission is dependent on the heating rate, the authenticity test result could be invalidated due to underestimation of the signal intensity. In this work, the percentage of signal intensity loss is investigated through the combination of a dynamic electro-mechanical model and a typical TL glow curve simulation. After first modelling the drilling procedure to estimate the maximum temperature reached, the optimal parameters that should be used during the sampling phase are checked by simulations together with an evaluation of the correlated signal losses.</span></p>
Highlights
Thermoluminescence testing (TL) has for many years been a routine methodology for dating and verifying the authenticity of terracotta works of art
The method is applied in three different experimental conditions with three metal bits with diameters equal to 2 mm, 3 mm and 5.5 mm. With these three configurations, called Drill 2, Drill 3 and Drill 5, the maximum temperatures reached were 130 °C, 82 °C and 60 °C, respectively. Using these values and applying the Arrhenius relation, we looked for ITL signal loss and simulated the consequent glow curves based on the Randall-Wilkins model and the Podgorsak approximation [11]
The values are expressed in terms of the TL intensity in the standard dating procedure, in which the powder of the sample is obtained by grinding the sample at room temperature. These values are reported in Figure 2; the decreasing of TL intensity as a function of drilling temperature is evident, and the effect is stronger for lower TL peak temperatures
Summary
Thermoluminescence testing (TL) has for many years been a routine methodology for dating and verifying the authenticity of terracotta works of art. Authenticity tests are used to distinguish between old (original) and new (fake) ceramic art objects through different sets of ITL measurement These sets consist of heating at a constant rate ( ), recording the natural ITL signals (natural glow curve) and exposing the sample to a calibration dose of beta radiation, preferably at a level comparable to its natural dose. The results presented in Gueli et al [30] fixed the basis for a more generalised model and a study of the effects of temperature on the TL authenticity tests In this context, this paper addresses these specific points and improves the state of the art by presenting a more exhaustive model of the entire drill-based architecture that can simulate any loss of the TL signal due to heating during sampling. The effects of the temperature reached during drilling in terms of TL signal loss in the collected sample have been simulated on the basis of the typical peaks of quartz crystalline inclusions
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