Recent improvements and applications of the LNS portable PIXE system

In the 1996 the feasibility of a portable PIXE has been demonstrated and a system has been realized thanks to a collaboration between the Laboratori Nazionali del Sud of Catania and the CEA-DIMRI of Saclay. The 210Po alpha-emitter of 37 MBq was used as a source for X-ray fluorescence excitation of the chemical elements present in the sample. More recently important improvements have been introduced: the actual system is able to detect elements as light as Na, to reach good energy resolution (140 eV at 5.9 keV) and to obtain good statistics in a reasonable measurement time (typically 15 min) for major elements when a freshly produced source is used. Due to the stability of the experimental parameters (incident energy, beam intensity, geometry), measurements are very reproducible and absolute values of the concentration are easily obtained by using reference standard calibration samples. The GUPIX code is used in the alpha-particle option. Accuracy and precision are obtained by using repeated measurements on different reference standards. Recent applications concern: the analysis of the bleu glazes of the Della Robbia terracotta at the National Museum of Bargello in Florence, the pigments characterization of a Pontificale of the XII century, the characterization of the silver patina in ancient coins. Some applications in the determinations of the S and Cl content in building stone materials and preliminary data in atmospheric pollutants are also presented.