Recent developments in atomic physics for the simulation of hot plasmas

Abstract

Simulations of plasmas in which atoms are not completely stripped require atomic data, like average charge, ionization energies, and radiative properties (emissivity, opacity). These depend on populations of energy levels. The basic framework for obtaining the latter is the collisional radiative model (CRM), which bridges the gap between the low-density Corona Equilibrium (CE) and Local Thermodynamic Equilibrium (LTE). However, for nearly all but the simplest ions, the number of relevant bound states and cross sections is prohibitive. In this review we summarize some recent methods for handling complex ions: By focusing on an exact evaluation of relevant information and ignoring unobservable features, unresolved transition arrays (UTA) are obtained. The supertransition arrays (STA) model combines many UTAs in LTE. The STA code was recently extended to a non-LTE CRM called SCROLL. Using these models could improve radiation simulation in hot plasmas, even for simple spectra.

Gershgorin and H theorems applied to collisional-radiative equilibrium model

“…This is what is implicitly hidden in the expression (23). This is not a straightforward task for complex codes such as those based on the superconfiguration approach [7,8] or for approach intending to explicitly check the validity of the configuration average procedure [9,10]. As for the total ion energy, we have other trends for the relaxation towards the steady-state.…”

“…Due to exponential decay (17), we do not reach explicitly zero for the H function and it is difficult to assign a definite value for the H function for which we Normalized rate of entropy production (21) is another stringent test of the internal consistency of a particular NLTE code. It may appear challenging to do this using complex NLTE codes based on the superconfiguration approach [7,8].…”

Ionization Balance in Inertial Confinement Fusion Hohlraums

“…The x-ray emission spectra from these highly ionized atoms are used for the diagnostics of high temperature fusion plasmas, solar flares, and short-wavelength plasma light sources. In particular, in indirect drive inertial confinement fusion (ICF) research, the averaged ionization stateZ is an important parameter because it determines basic physical quantities [1], i.e., acoustic velocities, electron densities, collision rates, and the thermal conductivity of the plasma, and is therefore closely linked to the understanding of the energetics of fusion plasmas.…”

Measurements and calculations of halfraum radiation drives at the omega laser

“…In the regions of the simulation expected to be in local thermodynamic equilibrium (LTE), the code uses the supertransition array (STA) opacity model [7,8].…”