A relativistic PIC model of nonlinear laser absorption in a finite-size plasma with arbitrary mass and density ratios

Abstract

AbstractIn this paper, we have studied the nonlinear laser absorption in a finite-size plasma, using a fully kinetic relativistic 1½-dimensional particle-in-cell simulation code, and shown that the rate in which laser absorption increases depends on the mass ratio (δ = m+/m−) and the equilibrium density ratio (α = n0+/n0− = z−/z+), respectively. This can be attributed to the essential effects of these parameters on the nonlinear phenomena related to the laser absorption such as phase-mixing and laser-scattering process. We have indicated that the reduction of the defined mass and density ratios increases the absorption rate in the finite-size plasma as long as the laser scattering from the plasma is not considerable. Moreover, the study of kinetic phase-space distributions indicates in a specific range of mass and density ratios a large amount of laser energy leads to arise a population of charged particles having directed kinetic energy along the laser direction. These simulation results are expected to be relevant to the experiments on the intense laser–plasma interactions with applications to the particle acceleration and fast ignition concept as well as to the astrophysical environments.