THE ANALYTICAL SIGNAL IN EPMA AND THE INFLUENCE OF THE ELECTRIC-FIELDCREATED BY THE PRIMARY BEAM

The electric field created by the primary electron beam inside an insu lator may change the analysed X-ray signal compared to that from a con ductor. It is assumed that homogeneous charge buildup occurs inside th e excited volume, Distributions of slowed down primary electrons are c alculated by the Monte Carlo method for light and heavy element sample s at both 10 keV and 50 keV. Because the incoming electron will be aff ected by the Bethe stopping power and the electric field it is advanta geous to express the former in V/m to explain the qualitative features of the electric field's influence. A few distribution functions were calculated to estimate the lowest value of electric field that would b e necessary in the sample to influence the analytical signal.