Amplification due to Two-Stream Instability of Self-Electric and Magnetic Fields of an Ion Beam Propagating in Background Plasma

TL;DR

This paper investigates how the two-stream instability affects the electromagnetic fields and focusing of ion beams in plasma, using simulations to identify conditions that minimize defocusing forces.

Contribution

It provides a detailed analysis of the scaling of instability-driven fields and identifies plasma parameters that reduce defocusing of ion beams.

Findings

Self-electromagnetic fields grow with plasma density and ion mass.

Certain plasma parameters can significantly reduce defocusing forces.

Simulation results guide optimal conditions for beam propagation.

Abstract

Propagation of charged particle beams in background plasma as a method of space charge neutralization has been shown to achieve a high degree of charge and current neutralization and therefore enables nearly ballistic propagation and focusing of charged particle beams. Correspondingly, use of plasmas for propagation of charged particle beams has important applications for transport and focusing of intense particle beams in inertial fusion and high energy density laboratory plasma physics. However, the streaming of beam ions through a background plasma can lead to development of the two-stream instability between the beam ions and the plasma electrons. The beam electric and magnetic fields enhanced by the two-stream instability can lead to defocusing of the ion beam. Using particle-in-cell (PIC) simulations, we study the scaling of the instability-driven self-electromagnetic fields and consequent defocusing forces with the background plasma density and beam ion mass. We identify plasma parameters where the defocusing forces can be reduced.