A Scattered-Field Formulation for Coupled Geometric Wakefield and Space Charge Field Simulations in Particle Accelerators

We propose a self-consistent simulation model for particle beams in accelerators, which includes the impact of electromagnetic wakefields caused by the geometry of the accelerator chamber. The method is based on a scattered-field formulation for the beam-driven Maxwell's equations. The total electromagnetic field seen by the particles is obtained as the solution of two coupled problems: a purely wakefield problem and a space charge field problem, where for each of these problems, specialized and numerically efficient approaches can be used. To assess the accuracy of the method, we compare simulation results with the analytical solution for a relativistic beam in a uniform accelerator pipe. The numerical efficiency of the method is, furthermore, demonstrated in the beam dynamics study of the multi-cell RF photo-gun installed at the SuperKEK collider facility. We show that electromagnetic wakefields have a non-negligible impact on the quality of the generated beam and, therefore, should be taken into account in the design of high-brilliance electron sources.