Field-reversed bubble in deep plasma channels for high quality electron acceleration

TL;DR

This paper investigates hollow plasma channels for laser-driven electron acceleration, demonstrating improved energy gain, mono-energetic beams, and optimized bubble dynamics, leading to high-quality electron beams with minimal energy spread.

Contribution

It introduces a new approach using deep plasma channels that enhances bubble acceleration and derives scaling laws for optimized electron energy gain.

Findings

No optical shock or etching in hollow channels increases phase velocity.

Achieved 0.3% total energy spread in electron beams.

Optimized plasma profiles balance laser depletion and dephasing.

Abstract

We study hollow plasma channels with smooth boundaries for laser-driven electron acceleration in the bubble regime. Contrary to the uniform plasma case, the laser forms no optical shock and no etching at the front. This increases the effective bubble phase velocity and energy gain. The longitudinal field has a plateau that allows for mono-energetic acceleration. We observe as low as 10^{-3} r.m.s. relative witness beam energy uncertainty in each cross-section and 0.3% total energy spread. By varying plasma density profile inside a deep channel, the bubble fields can be adjusted to balance the laser depletion and dephasing lengths. Bubble scaling laws for the deep channel are derived. Ultra-short pancake-like laser pulses lead to the highest energies of accelerated electrons per Joule of laser pulse energy.