Experimental Demonstration of Dephasing Reduction in an Optically Guided Laser-Plasma Accelerator

TL;DR

This paper demonstrates experimentally that combining plasma density tapering with optical guiding in laser-plasma accelerators reduces dephasing, significantly increasing electron beam energy beyond previous limits.

Contribution

It introduces a novel experimental approach using plasma density tapering and optical guiding to extend acceleration length and improve electron energy in laser-plasma accelerators.

Findings

Achieved electron energies over 1.6 GeV, a 40% increase over constant-density setups.

Particle-in-cell simulations confirm the roles of delayed injection, nonlinear laser evolution, and self-focusing.

Demonstrated the effectiveness of combined density tapering and optical guiding in dephasing reduction.

Abstract

Laser-plasma accelerators offer a compact means of producing high-energy electron beams, but their performance is fundamentally limited by dephasing between the accelerated electrons and the plasma wave. To overcome this limitation, we investigate the combination of plasma density tapering and optical guiding to extend the effective acceleration length. Using a Joule-class femtosecond laser coupled into an optical-field-ionized plasma waveguide with a controlled density gradient, we experimentally achieve electron beam energies exceeding 1.6 GeV, a 40% increase compared to the constant-density case. Particle-in-cell simulations reproduce the main experimental features and reveal the central roles of delayed injection, nonlinear laser evolution, and self-focusing in enhancing energy gain.