Sustained electron self-injection in an evolving ellipsoid bubble for laser-plasma interaction

TL;DR

This paper investigates a new sustained electron self-injection mechanism in an evolving ellipsoid bubble during laser wakefield acceleration, revealing electrons can be trapped near the axis and continue injection after initial stopping, leading to high-charge electron beams.

Contribution

The study introduces a novel self-injection mechanism in an evolving ellipsoid bubble, confirmed by simulations, that sustains electron injection and enhances beam charge in laser-plasma interactions.

Findings

Electrons near the laser axis can be trapped in an expanding bubble.

Self-injection persists even after initial injection stops.

The mechanism produces high-charge electron beams.

Abstract

Electron injection in an evolving ellipsoid bubble for laser wakefield acceleration is investigated by 2.5D PIC (Particle-In-Cell) simulation. Generally speaking, the self-injection electrons come from the position near the transverse radius in the bubble acceleration. However, we found the electrons near the laser axis also can be trapped into a longitudinal-expanding bubble. Moreover, this new self-injection mechanism is still existence after the electron self-injection stopped, which initially locates at near the bubble transverse radius. This phenomenon is confirmed through single-particle dynamic simulation. Besides, this new mechanism brings a high charge electron beam for acceleration, due to the sustained self-injection.