All-optical GeV electron bunch generation in a laser-plasma accelerator via truncated-channel injection

TL;DR

This paper presents a novel all-optical plasma channel scheme for generating high-quality GeV electron bunches with minimal energy spread, demonstrating experimental and simulation results for optimized acceleration.

Contribution

The work introduces truncated-channel injection for direct electron injection into laser-driven wakefields, achieving high-energy, low-spread electron bunches in a compact setup.

Findings

Generated 1.2 GeV electron bunches with 4.5% energy spread.

High-quality bunches require precise laser alignment and focusing.

Simulations suggest potential for 3.65 GeV bunches with longer channels.

Abstract

We describe a simple scheme, truncated-channel injection, to inject electrons directly into the wakefield driven by a drive pulse guided by an all-optical plasma channel. We use this approach to generate dark-current-free 1.2 GeV, 4.5 % relative energy spread electron bunches with 120 TW laser pulses guided in a 110-mm-long hydrodynamic optical-field-ionized (HOFI) plasma channel. Our experiments and particle-in-cell simulations show that high-quality electron bunches were only obtained when the drive pulse was closely aligned with the channel axis, and was focused close to the density down-ramp formed at the channel entrance. Start-to-end simulations of the channel formation, and electron injection and acceleration show that increasing the channel length to 410 mm would yield 3.65 GeV bunches, with a slice energy spread $\sim 5 \times 10^{-4}$.