A high-energy particle beam can be made to focus itself simply by 'bouncing' its own magnetic field off a stack of metal foils.
March 31, 2026
Original Paper
Strong-field focusing of high-energy particles in beam-multifoil collisions
arXiv · 2603.27692
The Takeaway
Usually, focusing 10-GeV electron beams requires massive, expensive magnets. This experiment proved that a beam can act like a lens for itself, using its own reflected energy to shrink its size, which could lead to much smaller and more powerful particle accelerators.
From the abstract
Extreme beams of charged particles and photons, reaching ultrahigh densities or producing intense gamma-ray bursts, are central to accelerator physics, laboratory astrophysics, and strong-field quantum electrodynamics research. Yet their generation is hindered by conventional focusing methods at multi-GeV energies that rely on massive magnetic assemblies, limiting compactness and attainable density. Here we report the first experimental observation of a fundamentally new focusing mechanism, in w