Modeling high intensity laser plasma interaction with the direct implicit method

Summary form only given. Implicit electromagnetic PIC codes permit to relax the stability constraints imposed by the resolution of the higher frequency electronic modes of the system. This is particularly valuable when modelling the interaction of high-intensity laser pulses with inhomogeneous over-critical plasmas. Here we will present the relativistic extension of the so-called direct implicit method including adjustable damping and high-order weight factors. This formalism was implemented in the 2Dx-3Dv code ELIXIRS, and benchmarked against explicit simulations for two kinds of physical problems : plasma expansion into vacuum and high intensity laser plasma interaction. In both cases, we will demonstrate the robustness of the implicit solver for rough discretizations. In particular, our new code is shown to capture the main features of laser-plasma interaction, whether average (laser absorption) or microscopic (bunched electron acceleration, ion acceleration). Eventually, the benefit of using second order weight factor will be highlighted.