Electron gun calculation in time domain

The method and code of electron gun calculation in time domain are presented. The Poisson equation in 2D axial region is solved by integral equation method. For modeling in time domain algorithm «step by step» is used. Three meshes — one spherical and two rectangular — are used for potential calculation and equation of motion solving. The consistent scheme of distribution between mesh points of particle charges and calculation of electric field acting on particle is used. This scheme eliminates effect «self-action» of particles. The cathode current is calculated as space charge limited flow. The initial thermal velocities are taken into account.