Driving positron beam acceleration with coherent transition radiation

TL;DR

This paper proposes a novel scheme using laser-driven electrons and coherent transition radiation to accelerate positrons to GeV energies, addressing key challenges in plasma wakefield positron acceleration.

Contribution

It introduces a combined method of electron-driven pair production and coherent transition radiation to efficiently accelerate positrons in a single setup.

Findings

Positron energies up to 1.5 GeV achieved in simulations.

Coherent transition radiation field reaches tens of GV/m.

Positron energy spread around 24.3%.

Abstract

Positron acceleration in plasma wakefield faces significant challenges since the positron beam must be pre-generated and precisely coupled into the wakefield, and most critically, suffers from defocusing issues. Here we propose a scheme that utilizes laser-driven electrons to produce, inject and accelerate positrons in a single set-up. The high-charge electron beam from wakefield acceleration creates copious electron-positron pairs via the Bethe-Heitler process, followed by enormous coherent transition radiation due to the electrons' exiting from the metallic foil. Simulation results show that the coherent transition radiation field reaches up to 10's GV m-1, which captures and accelerates the positrons to cut-off energy of 1.5 GeV with energy peak of 500 MeV and energy spread is about 24.3%. An external longitudinal magnetic field of 30 T is also applied to guide the electrons and positrons during the acceleration process. This proposed method offers a promising way to obtain GeV fast positron sources.