Characterization of laser-produced fast electron sources for fast ignition

Abstract

Laser-driven fast electron beams generated in planar foils or double cone targets have been characterized by means of two-dimensional particle-in-cell simulations. The laser beam focusing by the cone walls reduces the fast electron beam radius and increases the electron mean kinetic energy. Nevertheless, the beam divergence is high in both types of targets and can be split into two components: the dispersion angle and the radial velocity. The fast electron energy spectrum presents a power law profile. The effects of the fast electron source characteristics on the energy deposition in an ‘ideal’ precompressed inertial fusion target have been analysed. The radial velocity component of the fast electron beam significantly increases the energy required for ignition while the electron power law spectrum increases it slightly when compared with the standard exponential one.