Collisionless relaxation in non-neutral plasmas

TL;DR

This paper develops a theoretical framework to predict the final stationary states of non-neutral plasmas during collisionless relaxation, including effects of beam mismatch and phase separation, with applications to charged-particle beams.

Contribution

It introduces a quantitative theory for collisionless relaxation in non-neutral plasmas, accounting for density and velocity distributions, and explains phenomena like core-halo separation.

Findings

Fully matched beams relax to Lynden-Bell distribution.

Mismatch induces parametric resonances and core-halo phase separation.

The theory accurately predicts final stationary states.

Abstract

A theoretical framework is presented which allows to quantitatively predict the final stationary state achieved by a non-neutral plasma during a process of collisionless relaxation. As a specific application, the theory is used to study relaxation of charged-particles beams. It is shown that a fully matched beam relaxes to the Lynden-Bell distribution. However, when a mismatch is present and the beam oscillates, parametric resonances lead to a core-halo phase separation. The approach developed accounts for both the density and the velocity distributions in the final stationary state.