Bubble regime of plasma wakefield in 2D and 3D geometries

TL;DR

This paper develops a 2D model for plasma wakefield bubbles in nonlinear regimes, validates it with simulations, compares it to 3D structures, and proposes a method to generate quasi-2D bubbles in 3D plasmas.

Contribution

A new 2D analytical model for plasma wakefield bubbles in nonlinear regimes is derived and validated, with a novel approach to create quasi-2D bubbles in 3D plasmas.

Findings

2D bubble is elongated with stronger focusing forces in uniform plasma.

The structure of the accelerating field remains unchanged between 2D and 3D.

A method to generate quasi-2D bubbles in 3D plasma is proposed.

Abstract

Considering the popularity of two-dimensional particle-in-cell simulations, a 2D model of plasma wakefield in the strongly nonlinear (bubble) regime in transversely non-uniform plasma is developed. A differential equation for the boundary of the bubble in the 2D geometry is obtained, its analytic solution is derived. 2D particle-in-cell simulations are used to confirm the validity of our model. The results are compared to the bubble in the realistic 3D geometry. For uniform plasma, it is shown that the 2D bubble is elongated and has stronger focusing forces, while the structure of the accelerating field remains completely unchanged. A method of generating a quasi-2D bubble in the realistic three-dimensional geometry is proposed.