Evolution of equilibrium particle beams under external wakefields

TL;DR

This paper investigates how external wakefield perturbations affect the stability of ultrarelativistic particle beams in plasma, identifying critical phases and amplitudes that can lead to beam destruction.

Contribution

It provides a numerical analysis of the conditions under which perturbations can destabilize plasma-accelerated particle beams, highlighting the importance of wakefield phase and amplitude.

Findings

Certain wakefield phases are particularly destructive to the beam.

Low amplitude perturbations can destroy the beam at specific phases.

Perturbations exceeding the single bunch wakefield amplitude are always destructive.

Abstract

A beam of ultrarelativistic charged particles in a plasma can reach equilibrium with its own radial wakefield and then propagate with little change in shape. If some co-moving perturbation appears ahead of the beam, it may or may not destroy the beam with its wakefield, depending on the phase and amplitude of the wakefield. We numerically study which perturbations can destroy a single short bunch or a train of many short bunches at the parameters of interest for plasma wakefield acceleration in an axysimmetric configuration, and how fast. We find that there are particularly dangerous wakefield phases in which the beam can be destroyed by perturbations of very low amplitude. We also find that perturbations with an amplitude larger than the wakefield of a single bunch in the train are always destructive.