The chemical microanalysis of a surface by the Castaing technique is carried out by exciting characteristic X-ray emission from a selected point, located optically under a stationary electron beam about 1 μ in diameter. In many cases, the speed of working is greatly increased by the use of a scanning technique, which enables the surface distribution of a given element to be presented visually as an image on a cathode-ray tube screen. For quantitative analysis of a selected feature, accurate positioning of the beam may be carried out by reference to this image, or to a similar image showing topographical detail. The method has been applied to elements of atomic number 12 and above, in metallurgical, biological and mineralogical specimens. The paper deals with the principle, theory and design of an X-ray scanning microanalyser, and typical applications are illustrated by two examples.
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P. Duncumb (1959) studied this question.
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