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Latterly, PIXE using high-energy protons has been applied effectively for the qualitative analysis of archaeological and art objects, providing information from deep inside the object. This is due to the high cross-sections for the excitation of K-lines of heavy elements together with the large penetration depth of high-energy protons, resulting in analysable depth of up to several millimetres. After the extension of the GUPIX software package to proton energies of up to 100 MeV, quantitative analysis came within reach. Measurements on thin and thick metal targets, and also on alloy standards with known composition and various thickness, were performed. The concentrations obtained were compared with the certified values. The agreement was good for samples with a thickness of around 2 mm. However, for several centimetre thick samples, the heavy elements were overestimated when using the K-lines of these elements for the data evaluation. To clarify this, K-shell cross-section measurements were carried out for various Z. The measurements and the results are presented and discussed.

A measurement of the K‐shell fluorescence yield of silicon is undertaken in which identified sources of systematic errors in previous measurements are reduced or eliminated. This enables a stringent test of the only two sets of theoretical predictions available for atomic numbers less than 18. Our result ωK = 0.0495 ± 0.0015 is very slightly lower than the non‐relativistic Hartree‐Fock‐Slater (HFS) prediction of 0.0514. This stringent test of the HFS predictions helps to refine the fundamental parameter database of the X‐ray fluorescence analysis technique, whose importance for light elements is increasing. Our work indicates the need for new theoretical calculations of K‐shell fluorescence yields for these elements. Copyright © 2012 John Wiley & Sons, Ltd.