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Title: Experimental investigation of opacity models for stellar interior, inertial fusion, and high energy density plasmas

Abstract

Theoretical opacities are required for calculating energy transport in plasmas. In particular, understanding stellar interiors, inertial fusion, and Z pinches depends on the opacities of mid-atomic-number elements over a wide range of temperatures. The 150-300 eV temperature range is particularly interesting. The opacity models are complex and experimental validation is crucial. For example, solar models presently disagree with helioseismology and one possible explanation is inadequate theoretical opacities. Testing these opacities requires well-characterized plasmas at temperatures high enough to produce the ion charge states that exist in the sun. Typical opacity experiments heat a sample using x rays and measure the spectrally resolved transmission with a backlight. The difficulty grows as the temperature increases because the heating x-ray source must supply more energy and the backlight must be bright enough to overwhelm the plasma self-emission. These problems can be overcome with the new generation of high energy density (HED) facilities. For example, recent experiments at Sandia's Z facility [M. K. Matzen et al., Phys. Plasmas 12, 055503 (2005)] measured the transmission of a mixed Mg and Fe plasma heated to 156{+-}6 eV. This capability will also advance opacity science for other HED plasmas. This tutorial reviews experimental methods for testing opacitymore » models, including experiment design, transmission measurement methods, accuracy evaluation, and plasma diagnostics. The solar interior serves as a focal problem and Z facility experiments illustrate the techniques.« less

Authors:
;  [1];  [2];  [3]; ;  [4]; ; ;  [5]
  1. Sandia National Laboratories, Albuquerque, New Mexico, 87185-1196 (United States)
  2. University of Nevada, Reno, Nevada 89557 (United States)
  3. Lawrence Livermore National Laboratory, University of California, Livermore, California 94550 (United States)
  4. Prism Computational Sciences, Madison, Wisconsin 53703 (United States)
  5. CEA, DAM, DIF, F-91297 Arpajon (France)
Publication Date:
OSTI Identifier:
21277198
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 16; Journal Issue: 5; Other Information: DOI: 10.1063/1.3089604; (c) 2009 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ENERGY DENSITY; INERTIAL CONFINEMENT; LONGITUDINAL PINCH; OPACITY; PLASMA; STAR MODELS; X-RAY SOURCES

Citation Formats

Bailey, J. E., Rochau, G. A., Mancini, R. C., Iglesias, C. A., MacFarlane, J. J., Golovkin, I. E., Blancard, C., Cosse, Ph., and Faussurier, G.. Experimental investigation of opacity models for stellar interior, inertial fusion, and high energy density plasmas. United States: N. p., 2009. Web. doi:10.1063/1.3089604.
Bailey, J. E., Rochau, G. A., Mancini, R. C., Iglesias, C. A., MacFarlane, J. J., Golovkin, I. E., Blancard, C., Cosse, Ph., & Faussurier, G.. Experimental investigation of opacity models for stellar interior, inertial fusion, and high energy density plasmas. United States. doi:10.1063/1.3089604.
Bailey, J. E., Rochau, G. A., Mancini, R. C., Iglesias, C. A., MacFarlane, J. J., Golovkin, I. E., Blancard, C., Cosse, Ph., and Faussurier, G.. Fri . "Experimental investigation of opacity models for stellar interior, inertial fusion, and high energy density plasmas". United States. doi:10.1063/1.3089604.
@article{osti_21277198,
title = {Experimental investigation of opacity models for stellar interior, inertial fusion, and high energy density plasmas},
author = {Bailey, J. E. and Rochau, G. A. and Mancini, R. C. and Iglesias, C. A. and MacFarlane, J. J. and Golovkin, I. E. and Blancard, C. and Cosse, Ph. and Faussurier, G.},
abstractNote = {Theoretical opacities are required for calculating energy transport in plasmas. In particular, understanding stellar interiors, inertial fusion, and Z pinches depends on the opacities of mid-atomic-number elements over a wide range of temperatures. The 150-300 eV temperature range is particularly interesting. The opacity models are complex and experimental validation is crucial. For example, solar models presently disagree with helioseismology and one possible explanation is inadequate theoretical opacities. Testing these opacities requires well-characterized plasmas at temperatures high enough to produce the ion charge states that exist in the sun. Typical opacity experiments heat a sample using x rays and measure the spectrally resolved transmission with a backlight. The difficulty grows as the temperature increases because the heating x-ray source must supply more energy and the backlight must be bright enough to overwhelm the plasma self-emission. These problems can be overcome with the new generation of high energy density (HED) facilities. For example, recent experiments at Sandia's Z facility [M. K. Matzen et al., Phys. Plasmas 12, 055503 (2005)] measured the transmission of a mixed Mg and Fe plasma heated to 156{+-}6 eV. This capability will also advance opacity science for other HED plasmas. This tutorial reviews experimental methods for testing opacity models, including experiment design, transmission measurement methods, accuracy evaluation, and plasma diagnostics. The solar interior serves as a focal problem and Z facility experiments illustrate the techniques.},
doi = {10.1063/1.3089604},
journal = {Physics of Plasmas},
number = 5,
volume = 16,
place = {United States},
year = {Fri May 15 00:00:00 EDT 2009},
month = {Fri May 15 00:00:00 EDT 2009}
}
  • Analysis is presented of [ital K]- and [ital L]-shell spectra obtained from Ar and Xe dopants seeded into the fuel region of plastic capsules indirectly imploded using the Nova laser. Stark broadening measurements of the [ital n]=3-1 lines in H- and He-like Ar (Ar Ly-[beta] and He-[beta], respectively) are used to infer fuel electron density, while spatially averaged fuel electron temperature is deduced from the ratio of the intensities of these lines. Systematic variations in Ar spectral features are observed as a function of drive conditions. A spectral postprocessing code has been developed to simulate experimental spectra by taking intomore » account spatial gradients and line transfer effects, and shows good agreement with experimental data. It is shown that correct modeling of the x-ray emission requires a proper treatment of the coupled radiative transfer and kinetics problem. Continuum lowering effects are shown not to affect diagnostic line ratios, within the confines of a simple model. A recently developed diagnostic based on fitting measured line profiles of Ar He-[beta] and its associated dielectronic satellites to theory is shown to provide a simultaneous measure of electron temperature and electron density. [ital L]-shell Xe spectroscopy is under development as an electron temperature and electron-density diagnostic. Density and temperature sensitive ratios of spectral features each consisting of many lines have been identified. Observed Xe spectra from imploded cores show the same qualitative behavior with temperature, as predicted by model calculations of Xe emission spectra. Stark broadening of Ne-like Xe 4-2 lines appears viable as an electron density diagnostic for [ital N][sub [ital e]][similar to]10[sup 25] cm[sup [minus]3] and is under continuing investigation. (Based on the invited paper 8I3 at the 1992 APS/DPP annual meeting [Bull. Am. Phys. Soc. [bold 37], 1553 (1992)].)« less
  • We use an unresolved transition array model to investigate the opacities of high-Z materials and their mixtures which are of interest to indirect-drive inertial confinement fusion hohlraum design. In particular, we report on calculated opacities for pure Au, Gd, and Sm, as well as Au{endash}Sm and Au{endash}Gd mixtures. Our results indicate that mixtures of Au{endash}Gd and Au{endash}Sm can produce a significant enhancement in the Rosseland mean opacity. Radiation hydrodynamics simulations of Au radiation burnthrough are also presented, and compared with NOVA experimental data. {copyright} {ital 1997 American Institute of Physics.}
  • The design principles of a xenon gas shield device that is intended to protect optical components from x-ray induced opacity (“x-ray blanking”) have been experimentally demonstrated at the OMEGA-60 Laser Facility at the Laboratory for Laser Energetics, University of Rochester. A volume of xenon gas placed in front of an optical component absorbs the incoming soft x-ray radiation but transmits optical and ultra-violet radiation. The time-resolved optical (532 nm) transmission of samples was recorded as they were exposed to soft x-rays produced by a gold sphere source (1.5 kJ sr $-$1, 250–300 eV). Blanking of fused silica (SiO 2) wasmore » measured to occur over a range of time-integrated soft x-ray (<3 keV) fluence from ~0.2–2.5 J cm $-$2. A shield test device consisting of a 30 nm silicon nitride (Si 3N 4) and a 10 cm long volume of 0.04 bar xenon gas succeeded in delaying loss of transmission through a magnesium fluoride sample; optical transmission was observed over a longer period than for the unprotected sample. It is hoped that the design of this x-ray shield can be scaled in order to produce a shield device for the National Ignition Facility optical Thomson scattering collection telescope, in order to allow measurements of hohlraum plasma conditions produced in inertial confinement fusion experiments. Finally, if successful, it will also have applications in many other high energy density experiments where optical and ultra-violet measurements are desirable.« less