Speaker
Description
Improving the angular properties of laser-accelerated ion beams is essential for advancing the applicability of laser-driven ion sources. This work presents a comprehensive 2D and 3D particle-in-cell study of advanced plastic target designs aimed at reducing proton beam divergence while preserving high energies and particle numbers. The parametric study compares flat and curved foils with a range of rear-side channel geometries and identifies a flat foil with a straight cylindrical channel as the most effective configuration. The channel structure generates a long-lasting transverse electric field and, importantly, induces a distinctive electromagnetic field topology within the guiding cylinder. These self-generated fields include a magnetic quadrupole with a pronounced octupole component—an effect analogous to conventional multipole magnets, as demonstrated.
The resulting field configuration substantially reduces proton beam divergence and improves spatial uniformity across a broad energy interval. Additional investigations address several mechanisms that influence ion beam characteristics, including EM field inversions and the role of linear polarization direction. A realistic scenario was also explored by modelling the optimal channel target design with a preplasma generated by a laser prepulse, using density profiles imported from 2D MHD simulations. This enables a direct comparison between ideal and experimentally relevant laser contrast conditions.
These findings demonstrate that structured channel targets can act as passive beam-conditioning elements, offering a promising route toward controllable and application-ready laser-driven proton beams.