Works of art investigation with silicon drift detectors

Abstract

The X-ray fluorescence (XRF) spectroscopy analysis is a non-destructive technique widely used in archeometry to investigate the chemical composition of pigments, metal alloys and stones for restoration and historical investigation. The classical detection systems for archeometrical investigations utilize cryogenic detectors, like Si(Li) and HPGe, characterized by a satisfactory energy resolution (of the order of 140 eV FWHM at 6 keV). However, the requirements of liquid N 2 drastically limit the portability of such systems, limiting the possibility of making measurements “on the field”. Recently new silicon PIN diodes Peltier cooled were introduced, allowing the construction of portable instrumentation. However, their energy resolution (of the order of 250 eV FWHM at 6 keV) results in some cases unsatisfactory (for instance in the identification of light elements). Both the requirements of portability and good energy resolution are fulfilled by the silicon drift detector (SDD). The SDD, cooled by a Peltier element, can reach resolutions better than 150 eV FWHM at 6 keV. These features make the device ideal for portable high resolution XRF spectrometers. A portable XRF spectrometer was realized at the research laboratories of Politecnico di Milano, and used for investigation on different kinds of works of art. Experimental results obtained in analysis of paintings of different ages and of metal alloys performed directly “on the field” are summarized.