Emittance Preservation in an Aberration-Free Active Plasma Lens

TL;DR

This paper demonstrates that aberrations in active plasma lenses caused by plasma temperature nonuniformity can be fully suppressed by changing the gas species, enabling emittance preservation of electron beams.

Contribution

It provides the first direct measurement of aberrations in active plasma lenses and shows how to eliminate them by switching from helium to argon gas.

Findings

Aberrations are consistent with theoretical predictions.

Switching to argon suppresses aberrations.

Emittance preservation is achieved with argon-filled lenses.

Abstract

Active plasma lensing is a compact technology for strong focusing of charged particle beams, which has gained considerable interest for use in novel accelerator schemes. While providing kT/m focusing gradients, active plasma lenses can have aberrations caused by a radially nonuniform plasma temperature profile, leading to degradation of the beam quality. We present the first direct measurement of this aberration, consistent with theory, and show that it can be fully suppressed by changing from a light gas species (helium) to a heavier gas species (argon). Based on this result, we demonstrate emittance preservation for an electron beam focused by an argon-filled active plasma lens.