Perturbative Particle Simulations of Eigenmodes in High Intensity Charged Particle Beams

Two-dimensional body modes in high intensity charged particle beams are studied using the Beam Equilibrium Stability and Transport (BEST) code, which numerically solves the Vlasov-Maxwell equations using a low noise perturbative particle simulation method. The beam equilibrium is inhomogeneous in the radial direction and spatially uniform in the beam propagation direction. The beam equilibrium is determined self-consistently from the steady-state Vlasov-Maxwell equations for arbitrary space charge intensity, subject to transverse confinement by the applied smooth-focusing field. The two-dimensional body modes have an (r,z) mode structure localized inside the beam, with finite wavelength in the beam propagation direction. Wave-particle interactions, such as a strong Landau damping when the wave velocity in the beam frame matches the beam thermal velocity in the longitudinal direction, are numerically investigated for this family of eigenmodes.