Ion–electron two-stream instabilities in high intensity
heavy ion fusion beams, described self-consistently by the
nonlinear Vlasov–Maxwell equations, are studied using
a three-dimensional multispecies perturbative particle simulation
method. Large-scale parallel particle simulations are carried
out using the recently developed Beam Equilibrium, Stability,
and Transport (BEST) code. For a parameter regime characteristic
of heavy ion fusion drivers, simulation results show that the
most unstable mode of the ion–electron two-stream instability
has a dipole-mode structure, and the linear growth rate decreases
with increasing axial momentum spread of the beam particles
due to Landau damping by the axial momentum spread of the beam
ions in the longitudinal direction.