Evidence for high-energy and low-emittance electron beams using ionization injection of charge in a plasma wakefield accelerator

TL;DR

This paper demonstrates the experimental generation of high-energy, low-emittance electron beams via ionization injection in a plasma wakefield accelerator, achieving energies up to 30 GeV with improved beam quality.

Contribution

It provides experimental evidence of ionization injection producing high-energy, low-emittance electron beams in plasma wakefield acceleration, confirming theoretical predictions.

Findings

Injected electrons reach up to 30 GeV

Injected beam emittance is significantly smaller than the drive beam

Charge of injected electrons is tens of pC

Abstract

Ionization injection in a plasma wakefield accelerator was investigated experimentally using two lithium plasma sources of different lengths. The ionization of the helium gas, used to confine the lithium, injects electrons in the wake. After acceleration, these injected electrons were observed as a distinct group from the drive beam on the energy spectrometer. They typically have a charge of tens of pC, an energy spread of a few GeV, and a maximum energy of up to 30 GeV. The emittance of this group of electrons can be many times smaller than the initial emittance of the drive beam. The energy scaling for the trapped charge from one plasma length to the other is consistent with the blowout theory of the plasma wakefield.