Simulations of electron-beam transport in solid-density targets and the role of magnetic collimation

Abstract

Three-dimensional simulations of solid-target electron-transport experiments have been performed, using the hybrid-PIC code LSP. The experimentally observed fast-electron divergence half-angle of 16° in the target was reproduced assuming an initial divergence halfangle of ~56°, close to the value expected from the simple ponderomotive acceleration formula: θ1/2 = tan-1[√2/γ - 1)], where γ is the electron relativistic factor. The simulations accurately reproduce the details of the electron transport observed in the experiment. The electron beam propagates as an expanding annulus that breaks into filaments due to the resistive filamentation instability. The electron-beam partial collimation and annular propagation is due to the resistive azimuthal magnetic field generated at the outer edge of the electron beam. © 2010 IOP Publishing Ltd.