Laser-driven ion acceleration in long-lived optically shaped gaseous targets enhanced by magnetic vortices

TL;DR

This paper presents a method for high-repetition-rate laser-driven ion acceleration using optically shaped gaseous targets formed by intersecting blast waves, with magnetic vortices playing a key role.

Contribution

The study introduces a novel approach to shape long-lived, near-critical density targets with laser-driven shock waves, enabling efficient ion acceleration and magnetic vortex formation.

Findings

Achieved multi-MeV ion energy spectra in experiments.

Optimized target density profiles using 3D hydrodynamic simulations.

Identified Magnetic Vortex Acceleration as the primary mechanism.

Abstract

This research demonstrates high-repetition-rate laser-accelerated ion beams via dual, intersecting, counterpropagating laser-driven blast waves to precisely shape underdense gas into long-lived near-critical density targets. The collision of the shock fronts compresses the gas and forms steep density gradients with scale lengths of a few tens of microns. The compressed target persists for several nanoseconds, eliminating laser synchronization constraints. Measurements of multi-MeV ion energy spectra are reported. 3D hydrodynamic simulations are used to optimize the density profile and assess the influence of the Amplified Spontaneous Emission of the femtosecond accelerating laser pulse. A synthetic optical probing model is applied to directly compare simulations with experimental data. 3D Particle-In-Cell simulations reveal the formation of multi-kT, azimuthal magnetic fields, indicating Magnetic Vortex Acceleration as the main acceleration mechanism.