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  • 1
    Digitale Medien
    Digitale Medien
    Density sensitive line ratios for highly ionized atoms of the Cu i and Na i isoelectronic sequences (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3947-3952 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We discuss extreme ultraviolet and x-ray spectral lines emitted by ions of the Cu i and Na i isoelectronic sequences and show that certain intensity ratios of these lines are sensitive to electron density in the range from about 1018 to 1022 cm−3. These lines therefore provide density diagnostics for high-temperature plasmas. We illustrate the density dependence for four ions of the Cu i sequence (Z=60, 71, 82, 92) and seven ions of the Na i sequence (Z=32, 42, 52, 62, 72, 82, 92). We also show that the dependence of the ratios on electron temperature is not strong, and demonstrate that opacity can be kept small by employing the spot spectroscopy technique.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.346280
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  • 2
    Digitale Medien
    Digitale Medien
    Novel target configurations for selective ionization state studies in molybdenum (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5422-5427 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Details of experiments aimed at achieving low ionization state selectivity in molybdenum are presented. Targets are excited with a 10 J CO2 laser and the resultant vacuum ultraviolet spectrum (300–700 A(ring)) has been studied. Combinations of focal spot size, target depth, and target geometries are compared. Simple attenuation of energy is shown not to vary ionization stage composition significantly. Experiments conducted with grazing incidence targets result only in a hot plasma. Modular targets with cooling cylinders of various radii demonstrated good selectivity of the ionization states, but with low absolute signals. Finally, results from combinations of focal spot adjustment and radiative cooling illustrate increased control over desired plasma temperature and density for spectroscopic studies of molybdenum.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.347192
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  • 3
    Digitale Medien
    Digitale Medien
    A Fourier transform microscope for x-ray imaging : Proceedings of the 9th topical conference on high temperature plasma diagnostics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 5089-5093 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: This is a progress report on development of a new x-ray imaging system, called a Fourier transform microscope, intended for use with x-ray emitting targets in laser fusion experiments. It is being built by Naval Research Laboratory and Lawrence Livermore National Laboratory. The system works at energies from 3 to 7 keV. We describe the development of the design, which utilizes fine etched grids to extract Fourier amplitudes for the source brightness distribution at selected spatial frequencies. The finest grids in the prototype system will have rib dimensions of 2 μm. The prototype system is expected to achieve position resolution of 4 μm in 3–7 keV. Simulations of the expected imaging performance are presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1143501
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  • 4
    Digitale Medien
    Digitale Medien
    A review of the first ionization potential effect on elemental abundances in the solar corona and in flares (2002)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 9 (2002), S. 629-635 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The elemental composition of solar upper atmosphere plasmas was studied from spectra obtained by instruments aboard all major solar observatories that were launched into space in the last three decades. The studies show that the first ionization potential (FIP) of the elements has a profound effect on their abundance in the various solar upper atmosphere regions. In this paper we review properties of the FIP effect as they relate to coronal holes, quiet regions, active regions and flares and we show that although the derived compositions vary considerably with the type of plasma observed regularities in their behavior are emerging. The observed behavior may help identify the energy deposition mechanism that fuels the corona and solar flares. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1435000
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  • 5
    Digitale Medien
    Digitale Medien
    X-ray emission from plasmas created by smoothed KrF laser irradiation (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 3438-3447 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The x-ray emission from plasmas created by the Naval Research Laboratory Nike KrF laser [Phys. Plasmas 3, 2098 (1996) ] was characterized using imaging and spectroscopic instruments. The laser wavelength was 1/4 μm, and the beams were smoothed by induced spatial incoherence (ISI). The targets were thin foils of CH, aluminum, titanium, and cobalt and were irradiated by laser energies in the range 100–1500 J. A multilayer mirror microscope operating at an energy of 95 eV recorded images of the plasma with a spatial resolution of 2 μm. The variation of the 95 eV emission across the 800 μm focal spot was 1.3% rms. Using a curved crystal imager operating in the 1–2 keV x-ray region, the density, temperature, and opacity of aluminum plasmas were determined with a spatial resolution of 10 μm perpendicular to the target surface. The spectral line ratios indicated that the aluminum plasmas were relatively dense, cool, and optically thick near the target surface. The absolute radiation flux was determined at 95 eV and in x-ray bandpasses covering the 1–8 keV region. The electron temperature inferred from the slope of the x-ray flux versus energy data in the 5–8 keV region was 900 eV for an incident laser energy of 200 J and an intensity of ≈1013 W/cm2.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.871496
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  • 6
    Digitale Medien
    Digitale Medien
    High-resolution x-ray imaging of planar foils irradiated by the Nike KrF laser (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 1397-1401 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Thin plastic (CH) foils were irradiated by the Naval Research Laboratory Nike [Obenschain et al., Phys. Plasmas 3, 2098 (1996)] KrF laser and were imaged in the x-ray and extreme ultraviolet regions with two-dimensional spatial resolution in the 3–10 μm range. The CH foils were backlit by a silicon plasma. A spherically curved quartz crystal produced monochromatic images of the Si+12 resonance line radiation with energy 1865 eV that was transmitted by the CH foils. Instabilities that were seeded by linear ripple patterns on the irradiated sides of CH foils were observed. The ripple patterns had periods in the 31–125 μm range and amplitudes in the 0.25–5.0 μm range. The silicon backlighter emission was recorded by an x-ray spectrometer, and the 1865 eV resonance line emission was recorded by a fast x-ray diode. The multilayer mirror telescope recorded images of the C+3 1550 Å emission (energy 8.0 eV) from the backside of the CH foils. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.872315
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  • 7
    Digitale Medien
    Digitale Medien
    X-ray imaging of targets irradiated by the Nike KrF laser : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1099-1102 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Foil targets irradiated by the Naval Research Laboratory Nike KrF laser were imaged in the x-ray region with two-dimensional spatial resolution in the 2–10 μm range. The images revealed the smoothness of the emission from target and backlighter foils, the acceleration of the target foils, and the growth of Rayleigh–Taylor instabilities that were seeded by patterns on the irradiated sides of CH foils.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1147796
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  • 8
    Digitale Medien
    Digitale Medien
    Effect of resonance excitation due to dielectronic capture on the gain coefficients of selected transitions in Fe XVII (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 3984-3986 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: In previous papers, U. Feldman, J. F. Seely, and A. K. Bhatia [J. Appl. Phys. 56, 2475 (1984)] and A. K. Bhatia, U. Feldman, and J. F. Seely [At. Data Nucl. Data Tables (in press)] have calculated atomic data and gain coefficients for ions of the Ne I isoelectronic sequence. Their calculations of electron impact excitation rates were carried out in the distorted wave approximation. They did not include the effect of resonance excitation, i.e., dielectronic capture by a Ne-like ion followed by autoionization leaving the Ne-like ion in an excited state. In this paper, we use the recent calculations of this process by B. W. Smith, J. C. Raymond, J. B. Mann, and R. D. Cowan [Astrophys. J. (in press)] to explore the effect of resonance excitation on gain coefficient calculations for the ion Fe XVII. We find substantial differences (factors of about 1.3–3) between gain coefficient calculations with and without the inclusion of resonances at low temperatures. However, these effects are not important at the temperatures considered by Feldman, Seely, and Bhatia for Fe XVII.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.335573
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  • 9
    Digitale Medien
    Digitale Medien
    3s–3p laser gain and x-ray line ratios for the carbon isoelectronic sequence (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 3953-3957 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.336695
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  • 10
    Digitale Medien
    Digitale Medien
    Short wavelength laser calculations for electron pumping in Be I and B I isoelectronic sequences (18≤Z≤36) (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 2909-2915 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.335838
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