Modeling of population kinetics of plasmas that are not in local thermodynamic equilibrium, using a versatile collisional-radiative model based on analytical rates

Abstract

We discuss the modeling of population kinetics of nonequilibrium steady-state plasmas using a collisional-radiative model and code based on analytical rates (ABAKO). ABAKO can be applied to low-to-high Z ions for a wide range of laboratory plasma conditions: coronal, local thermodynamic equilibrium or nonlocal thermodynamic equilibrium, and optically thin or thick plasmas. ABAKO combines a set of analytical approximations to atomic rates, which yield substantial savings in computer running time, still comparing well with more elaborate codes and experimental data. A simple approximation to calculate the electron capture cross section in terms of the collisional excitation cross section has been adapted to work in a detailed-configuration-accounting approach, thus allowing autoionizing states to be explicitly included in the kinetics in a fast and efficient way. Radiation transport effects in the atomic kinetics due to line trapping in the plasma are taken into account via geometry-dependent escape factors. Since the kinetics problem often involves very large sparse matrices, an iterative method is used to perform the matrix inversion. In order to illustrate the capabilities of the model, we present a number of results which show that the ABAKO compares well with customized models and simulations of ion population distribution. The utility of ABAKO for plasma spectroscopic applications is also outlined.

Time-dependent and radiation field effects on collisional-radiative simulations of radiative properties of blast waves launched in clusters of xenon

“…The atomic processes included are the collisional ionization, three-body recombination,spontaneous decay, collisional excitation and deexcitation, radiative recombination, electron capture and autoionization. The calculation of the rate coefficients of these atomic processes was made using ABAKO code [25], except the one for the spontaneous decay which was obtained from FAC code. In ABAKO they are evaluated by means of analytical expressions widely used (see [25] for a more detailed description).…”

“…The calculation of the rate coefficients of these atomic processes was made using ABAKO code [25], except the one for the spontaneous decay which was obtained from FAC code. In ABAKO they are evaluated by means of analytical expressions widely used (see [25] for a more detailed description). To analyze the effect of the radiation from the shocked material in the radiative precursor, photoexcitation, photo-deexcitation and photo-ionization processes were also included in the CRM.…”

Atomic and optical properties of warm dense copper

“…The collisionalradiative kinetics models were used to calculate the level populations in non-LTE plasmas [21,[23][24][25][26]. When the collisional and radiative processes are important, the collisional-radiative approach based on rigorous atomic physics provides more realistic model to characterize and analyze the photon emission spectra, the equations of state, the ion composition, and the number of free electrons.…”

Parametrization of the average ionization and radiative cooling rates of carbon plasmas in a wide range of density and temperature

“…We perform an analysis of the influence of the thermodynamic regime in these quantities and we also present a parametrization of the cooling rate obtained by fitting bi-dimensional polynomial expressions (depending on the electron density and temperature) to our calculations which is valid in a wide range of electron temperatures (1-1000 eV) and electron densities (10 10 -10 21 cm" 3 ) covering CE, LTE and NLTE regimes. All the calculations presented in this work were made using ABAKO/RAPCAL computational package [34][35][36] which is briefly described in the next section. In Section 3 the analysis of the monochromatic emissivity, the radiative power loss and the cooling rate is made and the parametrization of the average ionization and the cooling rate is also presented.…”