Incident angle effect of the primary beam upon the mean depth of electrons in a target

When a target is bombarded by a mono-energetic beam, it emits several signals (back-scattered and secondary electrons, electromagnetic rays: X-rays, ir, uv, ...). Qualitative electron-probe microanalysis is based on the measurement of some radiation X. The X radiation intensity depends on the initial energy of the incident beam, on the element concentration which corresponds to the radiation, and, on the direction of the incident beam with regard to the plane surface of the target. Few programs study the effect resulting from varying the beam incidence angle. It is important to know to what extent parameters of microanalysis are effected by changes in the beam incidence angle. In this paper, we attempt to study the mean depth reached by incident electrons in a semi-infinite target. In fact, the absorption factor increases when the incidence angle decreases: this is because characteristic X-rays are generated closer to the target surface.