PIXE (Particle‐Induced X ‐Ray Emission)

Abstract

Abstract Particle‐induced X‐ray emission (PIXE) is the most popular among the ion beam analysis (IBA) techniques, which are based on the use of the specimen to be analyzed as a target for a beam of accelerated particles. The detection of the radiation induced by the beam bombardment is then used to discriminate and quantify the presence of the different elements in the specimen. In PIXE, what is exploited is in particular the X‐rays emitted from the target, whose energies are characteristic of the emitting atomic species. After a general, simple description of the main features of PIXE, with a short historical overview and a brief comparison to other X‐ray fluorescence (XRF) techniques, the article covers in greater depth all the specific aspects of this “nuclear” technique. The basic aspects of X‐ray emission from the atoms are first recalled; then, the extraction of quantitative compositional data from thin and thick specimens is explained, and a discussion is given of the excellent performance of PIXE in terms of minimum detection limits (MDLs), and of the factors affecting them. A technical description then follows of how proper beams for PIXE are produced and of the experimental set‐ups commonly used, with particular emphasis on the external‐beam arrangements. The X‐ray detector characteristics, the electronics for constructing the energy spectra, and the software processes for their deconvolution, leading to the extraction of quantitative data, are then briefly described. The last section surveys the main analytical applications of PIXE in various fields (environmental monitoring, biomedicine, earth sciences, cultural heritage), with no intent of exhaustiveness but rather with the purpose of focusing on when and why PIXE may be particularly suitable in each of them.