Advances in Elemental Analysis by Proton-Induced X-Ray Emission.

This thesis is devoted to the study of four areas in the development of proton-induced X-ray emission (PIXE), namely: (a) PIXE accuracy; (b) PIXE analytical sensitivity; (c) PIXE precision and (d) nuclear microprobe development. A novel approach to study the spectral response of a Si(Li) detector using monoenergetic photons is presented. The resulting improvement in PIXE accuracy (via spectrum deconvolution) is shown by obtaining high quality fits of single-element spectra obtained from both thin and thick targets. From these fits, a measurement of the K(beta) to K(alpha) intensity ratios by proton excitation is obtained. These ratios follow the smooth trend of previous experimental works using photon and electron excitations and are in contrast with the widely scattered values observed for proton ionization in earlier works. These developments will improve the PIXE database. The first comprehensive study of minimum detection limits (MDL) using protons impinging on thick specimens is presented and the different factors affecting their values discussed. In general, MDL values below 100 ppm by weight have been found for single trace elements in single element matrices. A guide for obtaining the minimum MDL's is provided. A test of the precision of thick-target PIXE analysis is made by analysing two samples and comparing the results with the certified one. One of these cases is a major element analysis and the other a trace element analysis. The good agreement obtained enhances confidence in this analytical technique. The design of the proton microprobe beam-line and the dedicated irradiation chamber for the analysis of mineral specimens at the proposed Guelph microprobe facility is presented. The improvements in PIXE analysis obtained in this thesis will be employed in this particular application.