The present invention relates to a method and system for automatically focusing an electron beam. Such an invention is based on a Faraday Cup diagnostic system, often a Modified Faraday Cup (MFC) system that enables tomographic reconstruction of the beam so as to measure beam parameters. Such a reconstruction method and system is automated using a servo-feedback loop to determine, for example, power distributions of the beam so as to provide appropriate adjustments to system controls to enable desired beam focus conditions.
 The United States Government has rights in this invention pursuant to Contract No. W-7405-ENG-48 between the United States Department of Energy and the University of California for the operation of Lawrence Livermore National Laboratory.