Inverse bremsstrahlung absorption with full electron-electron collisions operator

Abstract

A two-dimensional Fokker-Planck program is developed, in which full e-e collisions are taken into account self-consistently with arbitrary anisotropy of electron distribution function (EDF), to investigate inverse bremsstrahlung and the evolution of EDF. The numerical results show that e-e collisions will enhance inverse bremsstrahlung absorption. The evolution of EDF can be divided into two stages distinguished by different absorption rates. During the first stage, an initially Maxwellian EDF transforms rapidly into an anisotropic one with two temperatures. With the increase of anisotropy, the absorption rate decreases dramatically while the contribution ratio of e-e collisions increases rapidly. In particular, we find that with the increase of ion charge state Zi the contribution ratio of e-e collisions increases in the high laser frequency regime, while it decreases in the low frequency regime.