Excitation of long solitary waves in a neutralizing ion beam

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., electrostatic-solitary-waves (ESWs) were observed for such a setup in a 2D ion beam where the ESWs slowed the beam neutralization process. 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 a 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.