M.E. Sherrill

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.

Radiative Losses of Solar Coronal Plasmas

A comprehensive set of calculations of the radiative losses of solar coronal plasmas is presented. The Los Alamos suite of atomic structure and collision codes is used to generate collisional data for 15 coronal elements. These data are used in the Los Alamos plasma kinetics code ATOMIC to compute the radiative power loss as a function of electron temperature. We investigate the sensitivity of the loss curves to the quality of the atomic data and changes in the coronal elemental abundances, and we compare our results 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...

Conceptual design of initial opacity experiments on the national ignition facility

R. F. Heeter1,†, J. E. Bailey4, R. S. Craxton5, B. G. DeVolder2, E. S. Dodd2, E. M. Garcia5, E. J. Huffman3, C. A. Iglesias1, J. A. King3, J. L. Kline2, D. A. Liedahl1, P. W. McKenty5, Y. P. Opachich3, G. A. Rochau4, P. W. Ross3, M. B. Schneider1, M. E. Sherrill2, B. G. Wilson1, R. Zhang5 and T. S. Perry2 1Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94550, USA 2Los Alamos National Laboratory, Los Alamos, NM 87545, USA 3National Security Technologies, Livermore, CA 94550, USA 4Sandia National Laboratories, Albuquerque, NM 87185, USA 5Univ. of Rochester Laboratory for Laser Energetics, Rochester, NY 14623, USA

X-ray line polarization spectroscopy of Li-like Si satellite line spectra

We apply the magnetic-sublevel atomic kinetics model POLAR to the calculation of polarization properties of satellite lines in Li-like Si driven by subpicosecond-duration laser pulses. We identify spectral lines whose polarization can serve as a marker of plasma anisotropy due to anisotropy in the electron distribution function. We also discuss the utility and limitations of ur current theoretical approach and point out possible future improvements and directions.

Atomic physics modeling of transmission spectra of Sc-doped aerogel foams to support OMEGA experiments

We present synthetic transmission spectra generated with PrismSPECT utilizing both the ATBASE model and the Los Alamos opacity library (OPLIB) to evaluate whether an alternative choice in atomic data will impact modeling of experimental data from radiation transport experiments using Sc-doped aerogel foams (ScSi6O12 at 75 mg/cm3 density). We have determined that in the 50-200 eV Te range there is a significant difference in the 1s-3p spectra, especially below 100 eV, and for Te = 200 eV above 5000 eV in photon energy. Examining synthetic spectra generated using OPLIB with 300 resolving power reveals spectral sensitivity to Te changes of ∼3 eV.

Progress of the LANL Low Temperature/Low Frequency Air Opacity Project - Optical Theory for HET-project: an update, April 2015

Light radiated from a hot, opaque thermal emitter originates mostly from near the surface at which the object becomes opaque (the surface of last scattering). To be specific, we define the “optical surface” as the surface at which the optical depth, as observed from a detector, takes on the value of 1. The optical depth along a line of sight depends on the wavelength dependent. Accumulating light in different spectral bands, spectral detector then records light from different surfaces, a structure that we can picture somewhat like the layers of an onion. The theoretical framework that predicts the emitted spectral signal is radioactive transfer.

Light element opacities of astrophysical interest from ATOMIC

We present new calculations of local-thermodynamic-equilibrium (LTE) light element opacities from the Los Alamos ATOMIC code [1] for systems of astrophysical interest. ATOMIC is a multi-purpose code that can generate LTE or non-LTE quantities of interest at various levels of approximation. Our calculations, which include fine-structure detail, represent a systematic improvement over previous Los Alamos opacity calculations using the LEDCOP legacy code [2]. The ATOMIC code uses ab-initio atomic structure data computed from the CATS code, which is based on Cowans atomic structure codes [3], and photoionization cross section data computed from the Los Alamos ionization code GIPPER [4]. ATOMIC also incorporates a new equation-of-state (EOS) model based on the chemical picture [5]. ATOMIC incorporates some physics packages from LEDCOP and also includes additional physical processes, such as improved free-free cross sections and additional scattering mechanisms. Our new calculations are made for elements of astrophysical interest and for a wide range of temperatures and densities.We present new calculations of local-thermodynamic-equilibrium (LTE) light element opacities from the Los Alamos ATOMIC code [1] for systems of astrophysical interest. ATOMIC is a multi-purpose code that can generate LTE or non-LTE quantities of interest at various levels of approximation. Our calculations, which include fine-structure detail, represent a systematic improvement over previous Los Alamos opacity calculations using the LEDCOP legacy code [2]. The ATOMIC code uses ab-initio atomic structure data computed from the CATS code, which is based on Cowans atomic structure codes [3], and photoionization cross section data computed from the Los Alamos ionization code GIPPER [4]. ATOMIC also incorporates a new equation-of-state (EOS) model based on the chemical picture [5]. ATOMIC incorporates some physics packages from LEDCOP and also includes additional physical processes, such as improved free-free cross sections and additional scattering mechanisms. Our new calculations are made for elements of as...

Target Fabrication of Opacity Experiments on Z for Weapons Science Applications

Abstract Opacity data are very important in high energy density physics experiments. Recent targets of alternating layers of either Al2Te3 or Mg/Sn with a CH tamper have been made for obtaining these data. These targets are geometrically simple in the half-moon configuration of the metal compound coating to the pure CH tamper but require stringent procedural requirements to fabricate to the purity requirements. These specific targets require mass ratios of elements that proved to be difficult to obtain while also having the requirement of being pinhole-free and oxygen-free.