Bright electron bunches from a plasma-wakefield accelerator with a steep density down-ramp.

Wood, J C; Boulton, L; Beinortaitė, J; Björklund Svensson, J; Bohlen, S; Boyle, G; Garland, J M; Gonzalez Caminal, P et al. · Nat Commun · 2026

basic_science · Level V

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Abstract

High-brightness electron bunches drive fundamental research in particle physics and photon science. Key to achieving a high brightness is to have a low transverse emittance, which ensures that the bunch can be tightly focussed. In radiofrequency accelerators a low initial emittance can be rapidly degraded due to space charge forces, which are greatly diminished once the electron bunch attains a relativistic velocity. A plasma accelerator can maintain orders-of-magnitude higher accelerating fields than radiofrequency accelerators, while multiple techniques exist to create a low emittance electron bunch directly inside the plasma accelerator structure. Plasma accelerators therefore offer a possibility to create high-brightness bunches in wakefields driven even by low-quality drive bunches. Here we demonstrate the injection and gigavolt-per-metre acceleration of electron bunches with mm-mrad normalised emittance, <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>O</mi></math> (10 pC/MeV) spectral density and per-cent-level energy spread, all with excellent reproducibility.