D.P. Kilcrease

The Los Alamos suite of relativistic atomic physics codes

The Los Alamos suite of relativistic atomic physics codes is a robust, mature platform that has been used to model highly charged ions in a variety of ways. The suite includes capabilities for calculating data related to fundamental atomic structure, as well as the processes of photoexcitation, electron-impact excitation and ionization, photoionization and autoionization within a consistent framework. These data can be of a basic nature, such as cross sections and collision strengths, which are useful in making predictions that can be compared with experiments to test fundamental theories of highly charged ions, such as quantum electrodynamics. The suite can also be used to generate detailed models of energy levels and rate coefficients, and to apply them in the collisional-radiative modeling of plasmas over a wide range of conditions. Such modeling is useful, for example, in the interpretation of spectra generated by a variety of plasmas. In this work, we provide a brief overview of the capabilities within the Los Alamos relativistic suite along with some examples of its application to the modeling of highly charged ions.

A NEW GENERATION OF LOS ALAMOS OPACITY TABLES

We present a new, publicly available set of Los Alamos OPLIB opacity tables for the elements hydrogen through zinc. Our tables are computed using the Los Alamos ATOMIC opacity and plasma modeling code, and make use of atomic structure calculations that use fine-structure detail for all the elements considered. Our equation of state model, known as ChemEOS, is based on the minimization of free energy in a chemical picture and appears to be a reasonable and robust approach to determining atomic state populations over a wide range of temperatures and densities. In this paper we discuss in detail the calculations that we have performed for the 30 elements considered, and present some comparisons of our monochromatic opacities with measurements and other opacity codes. We also use our new opacity tables in solar modeling calculations and compare and contrast such modeling with previous work.

Los Alamos Opacities: Transition from LEDCOP to ATOMIC

This paper discusses the development of the ATOMIC code, a new low to mid Z opacity code, which will replace the current Los Alamos low Z opacity code LEDCOP. The ATOMIC code is based on the FINE code, long used by the Los Alamos group for spectral comparisons in local thermodynamic equilibrium (LTE) and for non‐LTE calculations, utilizing the extensive databases from the atomic physics suite of codes based on the work of R. D. Cowan. Many of the plasma physics packages in LEDCOP, such as line broadening and free‐free absorption, are being transferred to the new ATOMIC code. A new equation of state (EOS) model is being developed to allow higher density calculations than were possible with either the FINE or LEDCOP codes. Extensive modernization for both ATOMIC and the atomic physics code suites, including conversion to Fortran 90 and parallelization, are under way to speed up the calculations and to allow the use of expanded databases for both the LTE opacity tables and the non‐LTE calculations. Future pl...

Fast electric microfield distribution calculations in extreme matter conditions

Abstract Spectral line shapes provide a powerful tool for characterizing strongly coupled plasmas that have become experimentally more accessible in recent years. Line shape calculations in turn require as input the electric microfield distribution at the emitting atom or ion. The APEX approximation for microfield distributions is computationally fast and suited for weakly as well as strongly coupled plasmas. The currently available APEX program, however, contains computationally difficulties that restrict its range of applicability. Consequently, the code has been improved removing many of its shortcomings. An important new feature is the incorporation of the HNC integral equation solution to the radial distribution functions necessary for the APEX approximation.

Model comparisons for high-Z non-LTE steady-state calculations

Abstract Advances in computer technology and code development have made it possible to perform plasma kinetics calculations based on high- Z atomic structure corresponding to different levels of detail. Various atomic models have been implemented in the Los Alamos suite of codes in recent years for performing detailed non-equilibrium kinetics calculations. These include non-relativistic configuration average models with unresolved transition arrays (UTA), detailed fine structure models including configuration interaction and intermediate coupling that are capable of achieving spectroscopic accuracy for low- Z plasmas, and fully relativistic configuration average models employing the concept of the unresolved transition array, UTA, for modeling high- Z plasmas. Fully relativistic fine structure calculations have also been implemented and used primarily for accuracy checks. In addition, the fractional occupation number method has been introduced in the relativistic structure code to reduce computational times without reducing data quality. Finally, we will discuss a method that has been developed to use the populations extracted from a non-relativistic kinetics calculation in a relativistic spectral simulation. The purpose of the present work is to compare the emission spectra predicted by the various models and methods using consistent sets of atomic electron configurations and cross-sections for a gold plasma.

Radiative properties of stellar plasmas and open challenges

The lifetime of solar-like stars, the envelope structure of more massive stars, and stellar acoustic frequencies largely depend on the radiative properties of the stellar plasma. Up to now, these complex quantities have been estimated only theoretically. The development of the powerful tools of helio- and astero- seismology has made it possible to gain insights on the interiors of stars. Consequently, increased emphasis is now placed on knowledge of the monochromatic opacity coefficients. Here we review how these radiative properties play a role, and where they are most important. We then concentrate specifically on the envelopes of β Cephei variable stars. We discuss the dispersion of eight different theoretical estimates of the monochromatic opacity spectrum and the challenges we need to face to check these calculations experimentally.

Interpretation of the BRITE oscillation data of the hybrid pulsator ν Eridani: a call for the modification of stellar opacities

The analysis of the BRITE oscillation spectrum of the main sequence early B-type star

Wider pulsation instability regions for β Cephei and SPB stars calculated using new Los Alamos opacities

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CHEMEOS: A New Chemical‐Picture‐Based Model for Plasma Equation‐of‐State Calculations

Eridani is presented. Only models with the modified mean opacity profile can account for the observed frequency ranges as well as for the values of some individual frequencies. The number of the

The ion electric microfield gradient joint probability distribution function for dense plasmas

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