K-edge radiography: Comparison of two detectors

Abstract

Non-invasive and non-destructive diagnostics represent an important resource for historians and conservators for a deep knowledge of cultural heritage materials. K-edge radiography allows to obtain an elemental mapping of painting layers. It is performed at Larix laboratory, in Ferrara, by quasi-monochromatic X-ray beams obtained via Bragg diffraction. This technique takes advantage of the sharp rise of X-ray absorption coefficient of the elements, the K-edge discontinuity. Working at different energies, below and above the K-edge peak, allows to make the recognition of the target element. Each pigment is characterized by one or more elements; mapping an element means finding the spatial distribution of that pigment. Two different detectors have been used to perform an efficiency comparison at different energies. A commercial Front Illuminated CCD, 3075 × 128 pixels by Hamamatsu and an Edge-on SSD detector, designed by the Department of Science and Advanced Technology of Piemonte Orientale University, 512 Si-strip, 300 × 100 μm2 , 1 cm thick. In this paper the elemental distributions on canvas test objects with different pigment layers are presente