Analytic model for electromagnetic fields in the bubble regime of plasma wakefield in non-uniform plasmas

TL;DR

This paper presents an analytic perturbation model for electromagnetic fields in the bubble regime of plasma wakefields, accounting for non-uniform plasmas and validated by PIC simulations.

Contribution

It introduces explicit expressions for electromagnetic fields throughout the bubble volume in non-uniform plasmas, including hollow channels, extending previous models.

Findings

Good agreement with 3D PIC simulations

Explicit field expressions for entire bubble volume

Application to non-uniform and hollow channel plasmas

Abstract

Based on a model of plasma wakefield in the strongly nonlinear (bubble) regime, we develop a lowest-order perturbation theory for the components of electromagnetic fields inside and outside the bubble using the assumption of small thickness of the electron sheath on the boundary of the bubble. Unlike previous models, we derive simple explicit expressions for the components of electromagnetic fields not only in the vicinity of the center of the bubble, but in the whole volume of the bubble (including areas of driving or accelerated bunches) as well as outside it. Moreover, we apply the results to the case of radially non-uniform plasma and, in particular, to plasma with a hollow channel. The obtained results are verified with 3D particle-in-cell (PIC) simulations which show good correspondence to our model.