Kinetic Modeling of Solitary and Surface Waves in 3D Beam Neutralization

Ion beams are used in various engineering applications such as particle accelerators, ion-thrusters, and ion-implantations. The electrons are introduced to neutralize the beam and reduce their divergence along the axis. This is most economically achieved by introducing electrons via an external filament source. However, in recent numerical works by Lan et al. [1] , [2] , electrostatic-solitary-waves (ESWs) were observed for such a setup in a 2D ion beam where the ESWs slowed the beam neutralization process [2] . We present a Particle-in-Cell [3] study of the beam neutralization in both 2D and 3D beams and show the formation of ESWs and their movement along the beam axis. Further, by performing theoretical analysis, we will show the uniqueness of these ESWs found in ion beams where a non-Maxwellian electron distribution allows for ESWs of large lengths to form. We will also present our findings on the long-wavelength cylindrical surface waves [4] found in our 3D simulations and report the change in their properties with the beam radii. The prediction of surface waves and their frequencies is vital in experimental diagnostics and passive measurements in plasma beams [5] .