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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5511-5518 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Extreme ultraviolet (XUV) spectral line emissivities, originating from resonant transitions with upper states excited mainly from ground or both ground and lowest metastable states by electron collisional excitations of highly ionized intrinsic impurities in tokamak plasmas, are linear functions of both electron density and temperature fluctuations, ñe and T˜e, when the fluctuations are small and at high frequency. Correlations between measured intensities of spectral lines can thus provide localized measurements of the fluctuations. Newly developed XUV monochromators of high throughput enable accurate and fast diagnostics of ñe and T˜e for the study of the tokamak plasma microturbulence.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 2248-2252 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The populations of the 72 levels belonging to the 2s22p3, 2s2p4, 2p5, 2s22p23s, 2s22p23p, and 2s22p23d configurations of the N i isoelectronic sequence have been calculated for the ions Ar xii, Ti xvi, Fe xx, Zn xxiv, and Kr xxx and for electron densities up to 1024 cm−3. Electron collisional monopole excitation from the 2s22p3 ground configuration to the 2s22p23p configuration contributes significantly to the populations of the excited levels and results in relatively large 2s22p23p populations. The population inversions and laser gain for transitions between the 2s22p23s and 2s22p23p configurations are calculated. It is also found that large population inversions and gain occur between levels in the 2s22p23p configuration and levels in the 2s22p23d configuration that cannot decay to the ground configuration by an electric dipole transition. For these potential laser transitions of the type 2s22p23p-2s22p23d, the reabsorption of the radiation from the lower laser level is less of a problem than for the 2s22p23s-2s22p23p laser transitions. The 2s22p23p 4P5/2-2s22p23d 4D7/2 and 2s22p23p 2F7/2-2s22p23d 2G9/2 transitions represent promising transitions for overcoming some of the problems of opacity in dense plasmas. At high electron densities where the excited levels become collisionally mixed, the intensities of the x-ray transitions from the 2s22p23p levels to the 2s2p4 levels decrease relative to the x-ray transitions from the 2s22p23s and 2s22p23d levels. The density dependence of these x-ray line ratios is presented.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 3953-3957 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The populations of the 46 levels belonging to the configurations 2s22p2, 2s2p3, 2p4, 2s22p3s, 2s22p3p, and 2s22p3d have been calculated for ions in the C I isoelectronic sequence with atomic numbers Z=18, 22, 26, 30, 34, and 36 and for electron densities from 1015 to 1022 cm−3. The populations of the 2s22p3p levels are relatively large owing to the large electron collisional monopole excitation rates from the ground configuration and to the small radiative decay rates to the ground configuration. This results in population inversions for transitions of the type 3s–3p. The gain coefficients for these transitions are determined and are compared to previous calculations. At high electron densities where collisional mixing of the excited levels becomes important, the intensities of the x-ray transitions from the 2s22p3p levels to the 2s2p3 levels decrease relative to the x-ray transitions from the 2s22p3s and 2s22p3d levels. The density dependence of these x-ray line ratios is also presented. These line ratios represent a promising diagnostic for electron density.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 2909-2915 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Level populations of the 2s3p and 2s23p configurations in ions of the Be I and B I isoelectronic sequences can be inverted, with respect to populations of the 2s3s and 2s23s configurations, by electron collisional pumping. In the case of B I ions, the process is analogous to the process for Ne-like ions, which has lately received considerable attention. In the case of Be I ions, the inversion is a consequence of the slow radiative decay of the 2s3p 3P2 and 2s3p 3P0 levels. Level populations are calculated for Be- and B-like ions with atomic number Z between 18 and 36. For each sequence, 20 levels are involved with principal quantum number n equal either to two or three. Using the level populations, gain coefficients are calculated for transitions of the type 2s3s−2s3p and 2s23s−2s23p. Finally, the opacity of the 2s2p−2s3s and 2s22p−2s23s transitions are discussed, for plasma parameters for which a reasonable gain can be achieved.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 3954-3958 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The intensities of x-ray transitions in highly charged ions in the Be i, B i, and Ne i isoelectronic sequences have been calculated as functions of electron density. The intensities of the transitions from the 2sn 2pm 3p configuration, relative to the intensities from the 2sn 2pm 3s and 2sn pm 3d configurations, are strong functions of electron density in high-density plasmas. The density sensitivity occurs at electron densities between 1016 cm−3 (for Si ions) and 1022 cm−3 (for Kr ions). Opacity is unimportant for plasma dimensions that are characteristic of dense laser-produced plasmas. These x-ray line ratios represent a promising new density diagnostic for high-density plasmas.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Recent atomic data have been used to analyze a solar flare spectrum obtained with the Goddard Space Flight Center's grating spectrometer on the OSO-5 satellite. There exist in the wavelength region 90–200 Å strong lines from each of the ions Fe xviii-Fe xxiv. The Fe xxi lines can be used as an electron density diagnostic for the 107 K plasma. From our analysis of a particular flare, we find a steep positive slope in the emission measure between 106.5 and 107.2 K and an electron density of ∼4 × 1011 cm−3 at 107 K. We emphasise the need for high spectral and spatial resolution observations of solar flares in this wavelength region, which has to date been largely neglected.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 96 (1985), S. 11-26 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A study of the expected intensities of the stronger solar neon-like ion emission lines, some not yet observed, is carried out to compare with the observational situation. The potential usefulness of the 2p 5 3s(3 P 2) - 2p 6 forbidden line as a density diagnostic is discussed and new electric quadrupole lines in the soft X-ray range are noted. ‘Observability diagrams’ are presented as a convenient overview of the known and unobserved lines. The S vii resonance lines appear to have anomalous intensities.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 182 (1998), S. 37-63 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The opacities of the Si iii resonance line at 1206.5 Å and component lines of the UV 4 multiplet near 1300 Å are analyzed and re-examined in published spectra, taking account of improved expressions for photon escape probabilities and making use of an intensity/linewidth analysis recently developed. Level populations and line intensities are computed to extend knowledge of the optically thin spectrum to lower densities. Diagnostic diagrams of line ratios are included. Opacities are found to be higher than in previous treatments.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 65 (1980), S. 181-196 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Predicted allowed and forbidden EUV line intensities of Fe xv and Ni xvii are presented in explicit graphical form, clarifying and extending the earlier treatment of Bely and Blaha (1968). In the case of the former ion a detailed comparison with available observations leads to questioning or rejection of some presently accepted line identifications (323.57 Å, 317.61 Å), and on the other hand suggests that a quiet Sun line at 304.853 Å is due to Fe xv. For the little known ion Ni xvii estimates of level structure and line wavelengths are given and a preliminary comparison is made with recent flare observations.
    Type of Medium: Electronic Resource
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