A Fast 3D Multigrid Based Space–Charge Routine in the GPT Code

Fast calculation of 3D non–linear space–charge fields is essential for the simulation of high–brightness charged particle beams. We report on our development of a new 3D space–charge routine in the General Particle Tracer (GPT) code. It scales linearly with the number of particles in terms of CPU time, allowing over a million particles to be tracked on a normal PC. The model is based on a non–equidistant multigrid Poisson solver that is used to solve the electrostatic fields in the rest frame of the bunch. Bunch lengthening and emittance growth calculations in a low–energy short electron bunch are chosen as an example of non–linear space–charge effects in a high–brightness photo–injector.