Generation and Transport of Fast Electrons in Laser Irradiated Targets at Relativistic Intensities

Abstract

The transport of relativistic electrons in solid targets irradiated by a short laser pulse at relativistic intensities has been studied both experimentally and numerically. A Monte‐Carlo collision code takes into account individual collisions with the ions and electrons in the target. A 3D‐hybrid code takes into account these collisions as well as the generation of electric and magnetic fields and the self‐consistent motion of the electrons in these fields. It predicts a magnetic guiding of a fraction of the fast electron current over long distances and a localized heating of the material along the propagation axis. In experiments performed at LULI on the 100 TW laser facility, several diagnostics have been implemented to diagnose the geometry of the fast electron transport and the target heating. The typical conditions were: E1 ⩽ 20 J, λ = 1 μm, τ ≈ 300 fs, I ≈ 1018−5.1019W/cm2. The results indicate a modest heating of the target (typically 20–40 eV over 20 μm to 50 μm), consistent with an acceleration of the electrons inside a wide aperture cone along the laser axis.