Phase Space Dynamics of Ionization Injection in Plasma Based Accelerators

TL;DR

This paper analyzes the phase space evolution of ionization injection in plasma wakefield accelerators, providing an analytic theory verified by simulations that explains emittance growth and how to produce ultra-low emittance beams.

Contribution

It introduces a comprehensive analytic model for phase space dynamics in ionization injection, validated by PIC simulations, advancing understanding of beam quality control in plasma accelerators.

Findings

Rapid emittance growth due to phase mixing

Oscillation, decay, and slow growth of emittance over time

Potential to produce ultra-low emittance beams

Abstract

The evolution of beam phase space in ionization-induced injection into plasma wakefields is studied using theory and particle-in-cell (PIC) simulations. The injection process causes special longitudinal and transverse phase mixing leading initially to a rapid emittance growth followed by oscillation, decay, and eventual slow growth to saturation. An analytic theory for this evolution is presented that includes the effects of injection distance (time), acceleration distance, wakefield structure, and nonlinear space charge forces. Formulas for the emittance in the low and high space charge regimes are presented. The theory is verified through PIC simulations and a good agreement is obtained. This work shows how ultra-low emittance beams can be produced using ionization-induced injection.