Ion motion in the wake driven by long particle bunches in plasmas

TL;DR

This paper investigates how ion motion in plasma wakefield accelerators affects the stability and efficiency of the acceleration process, revealing that ion motion can suppress instabilities but can be mitigated with heavier ions.

Contribution

It provides a theoretical framework for understanding ion dynamics in plasma wakefield accelerators and demonstrates mitigation strategies using heavier plasma ions.

Findings

Ion motion can suppress self-modulation instability.

Heavier plasma ions mitigate ion motion effects.

Simulations confirm early suppression of accelerating fields.

Abstract

We explore the role of the background plasma ion motion in self-modulated plasma wakefield accelerators. We employ J. Dawson's plasma sheet model to derive expressions for the transverse plasma electric field and ponderomotive force in the narrow bunch limit. We use these results to determine the on-set of the ion dynamics, and demonstrate that the ion motion could occur in self-modulated plasma wakefield accelerators. Simulations show the motion of the plasma ions can lead to the early suppression of the self-modulation instability and of the accelerating fields. The background plasma ion motion can nevertheless be fully mitigated by using plasmas with heavier plasmas.