Thick-target correction in PIXE for randomly inhomogeneous samples

Inhomogeneous structure in a thick sample presents a multitude of difficult problems in e.g. particle-induced X-ray emission (PIXE) analysis. The yiel d for the elements analysed will deviate from the homogeneous case because of unpredictable cross-sections, attenuation coefficients and stopping powe rs throughout the range of the impinging particle. In this paper, an attemp t is made to correct for these inhomogeneity effects for a particular type of inhomogeneities, namely for randomly distributed ones. A model based on a randomly distributed structure of inhomogeneities is employed to calculat e the deviation from the normal homogenous thick-target correction. In the model an average is calculated over a finite set of positions of the inclus ion. A critical parameter is the size of the beam spot, which must be suffi ciently large to allow the inclusions in the measured volume to be consider ed randomly distributed. The size and density of the inclusions are varied according to known properties of the specimens. The model can be further re fined according to the need of the actual application, and the principle of the approach is equally valid for other ion beam analysis (IBA) techniques as well as for e.g. XRF. (C) 2000 Elsevier Science B.V. All rights reserve d.