Influence of atomic kinetics on inverse bremsstrahlung heating and nonlocal thermal transport

Abstract

This paper describes a computational model that self-consistently combines physics of kinetic electrons and atomic processes in a single framework. The formulation consists of a kinetic Vlasov-Boltzmann-Fokker-Planck equation for free electrons and a non-Maxwellian collisional-radiative model for atomic state populations. We utilize this model to examine the influence of atomic kinetics on inverse bremsstrahlung (IB) heating and nonlocal thermal transport. We show that atomic kinetics affects non-linear IB absorption rates by further modifying the electron distribution in addition to laser heating. We also show that accurate modeling of nonlocal heat flow requires a self-consistent treatment of atomic kinetics, because the effective thermal conductivity strongly depends on the ionization balance of the plasma.

Non-thermal evolution of dense plasmas driven by intense x-ray fields

“…While PIC-based models are very capable in capturing the evolution of the electron distribution in time and in space, they lack the full predictive capability for detailed x-ray emission spectroscopy. In contrast, non-thermal collisional-radiative codes deploying a Vlasov-Boltzmann-Fokker-Planck equation to treat non-Maxwellian electrons [21] are able to treat a vast number of ionic charge configurations, essential for predicting x-ray spectroscopy, and allow us to investigate the effect of non-thermal distributions on spectroscopic experiments at FEL facilities.…”

Classical molecular dynamic simulations and modelling of inverse-bremsstrahlung heating in low Z weakly-coupled plasmas

“…In order to challenge these theoretical results, numerical evaluations of IB heating has been carried out but mostly using Fokker-Planck (FP) simulations [18][19][20][21][22]. These simulations require collision kernels to be specified which amounts to making assumptions at microscopic level.…”

Quantum Fokker-Planck Modeling of Degenerate Electrons

“…We also note that Monte Carlo collision algorithms which simulate Coulomb collisions can be extended to include quantum degeneracy effects, and these provide an alternative to the qFP approach. [27,28] The numerical scheme presented here is built upon previous work on nonequilibrium electron kinetics modeling [13,29]. For simplicity, we consider the case of a uniform and spatially homogeneous plasma.…”

“…Transport effects due to spatial inhomogeneity can be incorporated by employing the full spherical Harmonic decomposition of the velocity distribution function [1,30,31]. This was demonstrated for the case of classical FP equation [29], and can be extended to the qFP equation in a straightforward manner.…”