Title: CHEMEOS: A New Chemical-Picture-Based Model for Plasma Eq uat ion-of -St ate Calcu I at i ons A CHEMEOS: A New Chemical-Picture-Based Model for Plasma Equation-of-State Calculations

Abstract. We present the results of a new plasma equation-of-state (EOS) model currently under development at the Atomic and Optical Theory Group (T-4) in Los Alamos. This model is based on the chemical picture of the plasma and uses the free-energy-minimization technique and the occupationprobability formalism. The model is constructed as a combination of ideal and non-ideal contributions to the total Helmholtz free energy of the plasma including the effects of plasma microfields, strong coupling, and the hard-sphere description of the finite sizes of atomic species with bound electrons [ 1, 21. These types of models have been recognized as a convenient and computationally inexpensive tool for modeling of local-thermal-equilibrium (LIE) plasmas for a broad range of temperatures and densities [3]. We calculate the thermodynamic characteristics of the plasma (such as pressure and internal energy), and populations and occupation probabilities of atomic bound states. In addition to a smooth truncation of partition functions necessary for extracting ion populations from the system of Saha-type equations, the occupation probabilities can also be used for the merging of Rydberg line series into their associated bound-free edges [4]. In the low-density, high-temperature regimes the plasma effects are adequately described by the Debye-Huckel model and its corresponding contribution to the total Helmholtz free energy of the plasma. In strongly-coupled plasmas, however, the Debye-Huckel approximation is no longer appropriate. In order to extend the validity of our EOS model to strongly-coupled plasmas while maintaining the analytic nature of our model, we adopt fits to the plasma free energy based on hypernetted-chain and Monte Carlo simulations [S, 6,7]. Our results for hydrogen are compared to other theoretical models. Hydrogen has been selected as a test-case on which improvements in EOS physics are benchmarked before analogous upgrades are included for any element in the EOS part of the new Los Alamos opacity code ATOMIC

NLTE Opacities of Mid- and High-Z Cocktails

In this work we report on the development of a new method for computing mid-and high-Z NLTE opacities. A study has been performed using this method to assess the EOS and opacity sensitivities to the radiation field for both single species Au and multi-species SnNb and U{sub 3}Au plasma cocktails with an emphasis on moderately to highly ionized systems. Developed as a benchmark tool to assess both current and future in line NLTE opacity capabilities, we have applied this new approach to assess XSN spectral fidelity for Au at commonly expected NIF hohlraum conditions

Wider pulsation instability regions for

Aims. Our goal is to test the newly developed OPLIB opacity tables from Los Alamos National Laboratory and check their influence on the pulsation properties of B-type stars. Methods. We calculated models using MESA and Dziembowski codes for stellar evolution and linear, nonadiabatic pulsations, respectively. We derived the instability domains of β Cephei and SPB-types for different opacity tables OPLIB, OP, and OPAL. Results. The new OPLIB opacities have the highest Rosseland mean opacity coefficient near the so-called Z-bump. Therefore, the OPLIB instability domains are wider than in the case of OP and OPAL data

Polarization of Emission Lines from Beryllium- like Oxygen OV: Analysis Based on the Population-Alignment Collisional-Radiative Model Polarization of emission lines from beryllium-like oxygen OV: Analysis based on the Population-Alignment Collisional-Radi

Abstract Longitudinal alignment of OV triplet lines for the (2s3s 3 S 1 -2s3p 3 P 0,1,2 ) transitions is studied on the basis of a population-alignment collisional -radiative (PACR) model, which correlates quantitatively the observed polarization of emission lines from ions and atoms in a plasma with an anisotropy in the electron velocity distribution. The results are compared with measurements on the WT-3 tokamak at Kyoto University. The measured negative values of the longitudinal alignment are qualitatively explained from the anisotropic velocity distributions that have higher speed in the poloidal direction than that in the toroidal direction

Population Alignment Collisional Radiative Model for Helium-like Carbon: Polarization of Emission Lines and Anisotropy of the Electron Velocity Distribution Function in Plasmas

The polarization of emission lines from a plasma carries information about the anisotropic velocity distribution of electrons in the plasma, and thus polarization spectroscopy can give information that is inaccessible by other methods. We have developed a comprehensive population-alignment collisional-radiative (PACR) model code for helium-like carbon CV ions. This code is intended to correlate quantitatively the observed polarization of emission lines from the ions in a plasma with the anisotropy of the electron velocity distribution function. Specifically, the longitudinal alignment of CV triplet emission lines for the (1s2s ^3S_l - 1s2p ^3P_l,2) transitions are studied by this PACR model. The predominant process which produces alignment in the 1s2p ~3P_l,2 levels is the alignment production from the ground state, 1s2 ISI and from the metastable level, 1s2s ^3S_1. The alignment-production fluxes from these levels are in the opposite directions in the temperature range of practical interest, depending on the electron density n_e. When ne > 10^16 m^-3, the alignment-production flux from the metastable level is larger than that from the ground state. An anisotropic electron velocity distribution function that has higher values in the axial (toroidal) direction than in the radial (poloidal) direction produces negative longitudinal alignment of the emission lines, i.e., higher intensity of the linear polarized component in the radial direction than that in the axial direction

Effects of line shifts and the ion quadrupole contribution of spectral line asymmetries.

Line asymmetries and the corresponding shift of spectral lines due to the electron penetration of the radiator orbitals and the ion quadrupole contribution become more significant with increasing principal quantum number and increasing electron density. The mean field static shift due to electron penetration of the orbitals gives rise to an overall shift of the line to lower energy and a significant asymmetry near line center, but does not generate much redhlue far wing asymmetry. The ion quadrupole contribution results in a small blue shift of the spectral line and a small change in asymmetry near line center, but it gives rise to a significant redhlue wing asymmetry in the far wings of the line. Experimental data fiom recent spherical implosion experiments on OMEGA shows evidence of the mean field static shift and may also show the effects of level interactions between the Ar Lyman -{gamma}, -{delta}, -{var_epsilon} lines and also the Ar He -{gamma}, -{delta} lines

State-resolved Photodissociation and Radiative Association Data for the Molecular Hydrogen Ion

We present state-resolved (electronic, vibrational, and rotational) cross sections and rate coefficients for the photodissociation (PD) of H 2 + and radiative association (RA) of H-H + . We developed a fully quantum mechanical approach within the nonrelativistic Born-Oppenheimer approximation to describe H 2 + and calculate the data for transitions between the ground electronic state 1ss g and the 2ps u , 2pp u , 3ps u , 3pp u , 4ps u , 4fs u , 4fp u , and 4pp u electronic states (i.e., up to H 2 + n = 4). Tables of the dipole-matrix elements and energies needed to calculate stateresolved cross sections and rate coefficients will be made publicly available. These data could be important in astrophysical models when dealing with photon wavelengths (or radiation temperature distributions that are weighted toward such wavelengths) around 100 nm. For example, at these wavelengths and a material temperature of 8400 K, the LTE-averaged PD cross section via the (second electronically excited) 2pp u state is over three times larger than the PD cross section via the (first electronically excited) 2ps u state