Computational investigation of dissipation and reversibility of space-charge driven processes in beams

Collisionless charged particle beams are presumed to equilibrate via the long-range potential from the space charge. The exact mechanism for this equilibration, along with the question of macroscopic reversibility, has been uncertain, however. A number of computational approaches based on particle-in-cell (PIC) methods are presented which can facilitate the resolution of these questions. One such technique is the self-consistent tracking of individual particle orbits through the nonlinear potential formed by nonuniform charge density distributions. This orbit-tracking model differs from the particle-core model in that the sampled particles are systematically chosen from the actual particles in a fully self-consistent simulation. The results of this analysis are presented for a number of representative cases, and the implications of the study on the equilibration mechanism are discussed.