Opacity of shock-heated boron plasmas
- Univ. of Notre Dame, IN (United States)
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Standard measures of opacity, the imaginary part of the atomic scattering factor f2 and the x-ray mass attenuation coefficient μ/ρ, are assessed in shock-heated boron, boron carbide and boron nitride plasmas. The Hugoniot equation, relating the temperature T behind a shock wave to the compression ratio ρ/ρ0 across the shock front, is used in connection with the plasma equation of state to determine the pressure p, effective plasma charge Z* and the K-shell occupation in terms of ρ/ρ0. Solutions of the Hugoniot equation (determined within the framework of the generalized Thomas–Fermi theory) show that the K-shell occupation in low-Z ions decreases rapidly from 2 to 0.1 as the temperature increases from 20 eV to 500 eV; a temperature range in which the shock compression ratio is near 4. The average-atom model (a quantum mechanical version of the generalized Thomas–Fermi theory) is used to determine K-shell and continuum wave functions and the photoionization cross section for x-rays in the energy range ω = 1 eV to 10 keV, where the opacity is dominated by the atomic photoionization process. For an uncompressed boron plasma at T= 10 eV, where the K-shell is filled, the average-atom cross section, the atomic scattering factor and the mass attenuation coefficient are all shown to agree closely with previous (cold matter) tabulations [1, 2, 3]. For shock-compressed plasmas, the dependence of μ/ρ on temperature can be approximated by scaling previously tabulated cold-matter values by the relative K-shell occupation; yet, there is a relatively small residual dependence arising from the photoionization cross section. Attenuation coefficients μ for a 9 keV x-ray are given as functions of T along the Hugoniot for B, C, B4C and BN plasmas.
- Research Organization:
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA)
- Grant/Contract Number:
- AC52-07NA27344
- OSTI ID:
- 1557064
- Alternate ID(s):
- OSTI ID: 1637126
- Report Number(s):
- LLNL-JRNL-758940; 947182
- Journal Information:
- High Energy Density Physics, Vol. 31, Issue C; ISSN 1574-1818
- Publisher:
- ElsevierCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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