Dr
Aimé Matheron
(Helmholtz Institute Jena)
Focusing multi-GeV electron beams to extreme densities is central to accelerator physics, laboratory astrophysics, and strong-field quantum electrodynamics research. Conventional approaches relying on large magnetic assemblies are ultimately limited in achievable focusing power.
Here we report the first experimental observation of a fundamentally new focusing mechanism, in which a high-energy electron beam is focused by its own electromagnetic fields reflected from a stack of thin metallic foils via near-field coherent-transition-radiation. When the beam traverses a conducting foil, electromagnetic boundary conditions require the transverse electric field to vanish at the surface while reinforcing the magnetic field, resulting in a net focusing Lorentz force at the foil surface. Repeating this interaction across multiple foils produces strong focusing.
The experiment, performed at SLAC’s FACET-II facility, reveals strong, cumulative focusing across a broad range of beam configurations, enabled by the delivered 10 GeV, 1 nC, 10 Hz electron beam. The measurements closely agree with predictions from an analytical model and particle-in-cell simulations. These results demonstrate that multifoil focusing is a remarkably straightforward, self-aligned approach to extreme beam generation, opening a path to explore unprecedented regimes of beam-matter interaction and high-energy radiation.
Dr
Aimé Matheron
(Helmholtz Institute Jena)
Dr
Doug Storey
(SLAC National Accelerator Laboratory)
Dr
Max Gilljohann
(Laboratoire d’Optique Appliquée (LOA))
Sebastien Corde
(Laboratoire d’Optique Appliquée (LOA))
Sheldon Rego
(Laboratoire d’Optique Appliquée (LOA))
Alexander Knetsch
(SLAC National Accelerator Laboratory)
Brendan O'Shea
(SLAC National Accelerator Laboratory)
Chan Joshi
(University of California Los Angeles)
Chaojie Zhang
(University of California Los Angeles)
Christoph H. Keitel
(Max-Planck-Institut für Kernphysik)
Claire Hansel
(University of Colorado Boulder)
Claudio Emma
(SLAC National Accelerator Laboratory)
Erik Adli
(Department of Physics, University of Oslo)
Frederico Fiuza
(GPA/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico)
Gevy J. Cao
(Department of Physics, University of Oslo)
Igor Andriyash
(Laboratoire d’Optique Appliquée (LOA))
Ivan Rajkovic
(SLAC National Accelerator Laboratory)
Laurent Gremillet
(CEA, DAM, DIF)
Mark Hogan
(SLAC National Accelerator Laboratory)
Matteo Tamburini
(Max-Planck-Institut für Kernphysik)
Michael Litos
(University of Colorado Boulder)
Pablo San Miguel Claveria
(Instituto de Fusión Nuclear “Guillermo Velarde”, Universidad Politécnica de Madrid)
Spencer Gessner
(SLAC National Accelerator Laboratory)
Valentina Lee
(University of Colorado Boulder)
Viktoriia Zakharova
(Laboratoire d’Optique Appliquée (LOA))
Xavier Davoine
(CEA, DAM, DIF)
Yuliia Mankovska
(Laboratoire d’Optique Appliquée (LOA))
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