FLYCHK: Generalized population kinetics and spectral model for rapid spectroscopic analysis for all elements

Abstract

FLYCHK is a straightforward, rapid tool to provide ionization and population distributions of plasmas in zero dimension with accuracy sufficient for most initial estimates and in many cases applicable for more sophisticated analysis. FLYCHK solves rate equations for level population distributions by considering collisional and radiative atomic processes. The code is designed to be straightforward to use and yet is general enough to apply for most laboratory plasmas. Further, it can be applied for low-to-high Z ions and in either steady-state or time-dependent situations. Plasmas with arbitrary electron energy distributions, single or multiple electron temperatures can be studied as well as radiation-driven plasmas. To achieve this versatility and accuracy in a code that provides rapid response we employ schematic atomic structures, scaled hydrogenic crosssections and read-in tables. It also employs the jj configuration averaged atomic states and oscillator strengths calculated using the Dirac-Hartree-Slater model for spectrum synthesis. Numerous experimental and calculational comparisons performed in recent years show that FLYCHK provides meaningful estimates of ionization distributions, well within a charge state for most laboratory applications.

Advances in NLTE modeling for integrated simulations

“…For autoionization rates, we use the method of Chung et al [27]. These rates involve three states -the autoionizing state n, plus the lower and upper states i,j from the next ionized isosequence that provide a stabilizing transition.…”

“…Bauche et al [26] review autoionization and resonant capture, and discuss approximations for calculating these rates. Here, following the lead of Chung et al [27], we use the formulation developed by Sobel'man et al [28]. As shown in [27], this simple formula reproduces the results of detailed calculations very well.…”

“…Here, following the lead of Chung et al [27], we use the formulation developed by Sobel'man et al [28]. As shown in [27], this simple formula reproduces the results of detailed calculations very well. This result, combined with the ability to generate an atomic structure that includes autoionizing states, is perhaps the key piece in inexpensively calculating ionization balance for complex atoms.…”

A new set of relativistic screening constants for the screened hydrogenic model

“…This model determines the energy levels of an electronic configuration as a sum of hydrogenic one-electron energies that are computed with appropriate screened nuclear charges. The SHM used in the average ion model context provides electronic populations with good accuracy and it also allows computing radiative properties [1][2][3][4][5][6][7][8] such as the opacity or the emissivity, as well as thermodynamic properties such as the equation of state or the shock Hugoniot curves [9][10][11]. For this reason the model has been widely used in the simulation of inertial confinement fusion [12].…”

“…Nevertheless, some authors take them into account using the hydrogenic approximation with relativistic corrections [7,8], and others, use Dirac's relativistic energy expression for the hydrogen atom for the same purpose [1,20]. However, currently there does not exist a set of screening constants fit to energy values considering j-splitting.…”