Self-focusing of a modulated ribbon REB in dense plasma

A numerical experiment is described which permits the nonlinear dynamics of the interaction between a ribbon-shaped relativistic electron beam in the form of separate clumps and a dense plasma to be analyzed. The particle technique was used with periodic and open models to study the beam neutralization stage, the formation of potential wells, the compression of the clumps to high density, and the approach to a steady self-focused regime predicted by analytical theory. After the clumps reach equilibrium with the transverse field, low-frequency longitudinal pulsations develop in the plasma, corresponding to a periodic shift in the clumps and lagging in the accelerating phases of the wave. 16 refs., 9 figs