Element mapping by a scanning X-ray system

Physical surface analysis methods using charged particles on the excitation side can easily be applied to elemental distribution mapping. One common feature of all known methods is that they work on a micron scale, with respect to spatial resolution and investigated sample area. This paper deals with a new approach to the problem of element mapping using X-ray fluorescence radiation. In contrast to the well-known scanning procedures, this method allows the investigation of larger areas (several square centimetres) at lower spatial resolutions (> approximately 100 μm). The method applies a mechanical scanning device, a modern energy-dispersive detector and a computer. The scanning unit allows translation and rotation movements of the sample. By generating a line-shaped X-ray beam and translating the sample across the fixed X-ray strip while measuring the intensity of the fluorescence radiation in a specified energy window, one obtains a strip resolution of the species investigated. If many translation measurements are made under different angular orientations of the sample, a computer converts the strip resolutions of the scanning profiles into a point resolution of the specified element. The mathematical background is known in the literature as 'representation of a function by its line integrals' or 'image reconstruction from projections'. Computer simulation studies and experimental results are discussed. (author)