Speaker
Description
Determining plasma opacities requires knowledge of the electronic structure
of many atomic configurations. For dense plasmas, the number of configurations
required to accurately represent the plasma is often intractably large when using
methods that require explicit accounting of each configuration. The supercon-
figuration concept [1] allows one to use a representative atomic structure for
groups of configurations, and the super transition array (STA) technique [1,2]
then uses those superconfiguration structures to form an opacity that approxi-
mately retains the same statistical properties of opacities obtained using explicit
accounting methods. The cost of this STA approach is that many spectral lines
are merged into broader features, which reduces the number of so-called “win-
dows” of low opacity in between spectral lines. Though this loss of spectral
resolution is necessary to tractably account for the large number of configura-
tions found in plasmas, quantities such as the Rosseland mean opacity are very
sensitive to the absence of opacity windows. In this work, we build on prior
STA development [3] and present the results from our hybrid fine-structure and
STA approach, which uses superconfigurations to incorporate the influence of
more exotic configurations and splits configurations that are closer to the ground
state in energy into fine-structure levels. This hybrid approach gives an opacity
that combines the strength of the STA formalism to capture all possible con-
figurations with the increased spectral resolution obtained from fine-structure
transitions.
[1] A. Bar-Shalom et al, Phys. Rev. A 40, 3183-93 (1989).
[2] A. Bar-Shalom, J. Oreg, Phys. Rev. E 54, 1850-6 (1996).
[3] N. M. Gill, C. J. Fontes, C. E. Starrett, J. Phys. B 56, 015001 (2023).
| Presenting Author | Nathanael Gill |
|---|---|
| Presenting Author Email Address | ngill@lanl.gov |
| Presenting Author Affiliation | LANL |
| Country | United States of America |
| Presenting Author Gender | Male |
