Excitation of electrostatic solitary waves and surface waves in ion beam neutralization process

TL;DR

This paper reports the discovery of unusually long electrostatic solitary waves and surface waves during ion beam neutralization, highlighting the importance of 3D effects in wave excitation and electron dynamics.

Contribution

It introduces the observation of long ESWs and surface waves in ion beam neutralization through 2D and 3D Particle-in-Cell simulations, emphasizing the role of geometry.

Findings

Long ESWs are due to electron density perturbation compensation.

Surface waves are only observed in 3D simulations.

3D geometry allows high-energy electrons to excite surface waves.

Abstract

Unusually long electrostatic solitary waves (ESWs) are discovered in 2D and 3D Particle-in-Cell studies of the process of ion beam neutralization by electron emission from filaments. These ESWs are long because trapped and untrapped electron density perturbations nearly compensate each other. Surface waves were discovered in the process of neutralization but were only observed in 3D simulations. This is because the phase velocity of surface waves in a 2D geometry is higher than in 3D giving the high-energy electrons generated upstream near the electron source enough energy to excite such waves only in 3D cylindrical beams.