Positron acceleration by plasma wake fields driven by a hollow electron beam

TL;DR

This paper proposes a novel plasma wakefield acceleration scheme using hollow electron beams to efficiently accelerate positrons to high energies with high gradients and low energy spread.

Contribution

It introduces a hollow electron beam driver for positron acceleration, demonstrating high gradients and efficient energy transfer in plasma wakefield acceleration.

Findings

Achieved 10 GV/m accelerating gradients with hollow electron beams.

Successfully accelerated positrons from 23 GeV to 35.4 GeV.

Maintained low energy spread of 0.4% and small emittance.

Abstract

A scheme of wake field generation for positron acceleration using hollow or donut shaped electron driver beams is studied. An annular shaped, electron free region forms around a hollow driver beam creating a favorable region (longitudinal field is accelerating and transverse field is focusing and radially linear) for positron acceleration. Accelerating gradients of the order of 10 GV/m are produced by a hollow electron beam driver with FACET like parameters. The peak accelerating field increases linearly with the total charge in the beam driver while the axial size of the favorable region ($\sim$ one plasma wavelength) remains approximately fixed. The radial size drops with the total charge but remains large enough for the placement of a witness positron beam. We simulate an efficient acceleration of a 23 GeV positron beam to 35.4 GeV with a maximum energy spread of 0.4\% and very small emittance over a plasma length of 140 cm.