- Ben-Gurion UniversityDepartment of Electrical and ComputerEngineeringP.O. Box 653Beer-Sheva 84105, IsraelAbstract. Branching stochastic processes are used to describe randomsystems such as nuclear chain reactions, population development, andgene propagation. We show that the creation of a scanning-electron-microscope signal can be described as a branching stochastic process.A statistical model is described step by step, as a function of the physicalparameters of the process. Using the model, we propose a method fordetermining the unknown probability distribution of the secondary elec-tron emission. Using this method, a lognormal distribution is shown toapproximate the secondary electron emission well, and a Poisson distri-bution is shown to do so poorly.