Inhomogeneities of the Ancient Coin Composition: the Suggestion for a New non Destructive Analytical Method

The non-destructive techniques, generally used to analyse the ancient coins, XRF (X-Ray Fluorescence), PAA (Proton Activation Analysis) and NAA (Neutron Activation Analysis), are not able to distinguish between the contributions of the coin interior and its surface. In several cases, the surface composition is very different from the interior content. As an example, we will show the XRF results on the tin concentration in the surface of 26 Greek ancient bronze coins compared, in two cases, with the interior results. We propose a new non-destructive technique, the DPAA (Deep Proton Activation Analysis) method, which will permit to confine the analysis only in the interior region of the coins without interference with the surface.