One-dimensional focusing of an electron beam by a laser-driven cylindrical blowout wakefield in orthogonal configuration.

Laser plasma wakefields provide accelerating gradients 1000× greater than conventional RF cavities with strong transverse focusing forces, enabling compact beam control systems. Prior studies have primarily focused on collinear geometries, where the focusing force is radially symmetric, limiting directional control. In this work, we present a novel regime that forms a cylindrical blowout wakefield structure, enabling one-dimensional (1D) control over the focusing geometry for an orthogonally propagating beam. This regime is driven by a relativistic-intensity laser (a₀ ~ 1) with a pulse duration of 1–2 plasma wavelengths, which modifies the electron trajectories to generate a cylindrical wake. Particle-in-cell (FBPIC) simulations show that this regime exhibits focusing forces that mimic blowout behavior while producing a near-flat accelerating field. These combined features support asymmetric, i.e., 1D, transverse focusing. Experiments at ATF, BNL used a 2–3 TW, 2 ps, 9.2 μm CO₂ laser focused into a hydrogen gas jet at a plasma density of 3 × 10¹⁵ cm⁻³. A 50–60 MeV, 150–200 fs electron beam was used to probe the wake; imprinted deflection patterns were imaged downstream on YAG:Ce scintillator screens, measuring a focal length of ~1–2 cm. The results validate this regime and highlight its potential to scale for 100 GeV beam focusing in advanced accelerator systems.