Transverse space-charge modes in non-equilibrium beams

Abstract

Successful operation of a Heavy Ion Fusion driver requires knowledge of how the beam responds to various perturbations from equilibrium. Recently, simulations and experiments have verified predictions that space-charge-dominated beams can carry waves, observable as modulations in the particle density and temperature. Self-consistent simulations using the particle-in-cell code WARP explore the evolution and scaling of space charge modes, both in linear and circular machines. Examples of phenomena where these collective modes play a critical role are provided. In circular focusing arrays, the modes resonate when driven by lattice errors, at frequencies which depend on the space charge intensity. Collective modes are shown to lead to emittance exchange and energy equipartitioning in an anisotropic system. Scaling relations are determined for some of these effects.