Efficient Acceleration of High-Quality GeV-Electron Bunches in a Hybrid Laser- and Beam-Driven Plasma Wakefield Accelerator

TL;DR

This paper demonstrates a hybrid plasma accelerator scheme that significantly improves electron beam quality, energy transfer efficiency, and energy gain by combining laser wakefield and beam-driven plasma wakefield acceleration techniques.

Contribution

It introduces a hybrid LWFA-PWFA scheme with internal witness injection, achieving higher energy, reduced spread, and improved efficiency over previous methods.

Findings

Witness bunches with higher energy and lower spread

Energy transfer efficiency of about 20% from driver to witness

Energy transformer ratios approaching 2

Abstract

Plasma-based accelerators are compact and provide high gradients, yet their practical use has been limited by energy gain, stability, beam quality, and energy transfer efficiency. Here, we address several of these challenges simultaneously using a hybrid scheme in which an electron bunch from a laser wakefield accelerator (LWFA) drives a subsequent plasma wakefield accelerator (PWFA) stage with internal witness injection. Close to driver depletion in the PWFA stage, we obtain witness bunches with higher electron energy, reduced energy spread and divergence, and higher angular-spectral charge density compared to LWFA alone. We report energy transformer ratios approaching~2, and about 20\% of the initial energy in the drive beam was transferred to the witness bunch, thereby achieving a driver-to-witness energy transfer efficiency that largely surpasses that of all previous PWFA experiments.