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  • 1990-1994  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    X-ray spectroscopy of high-energy density inertial confinement fusion plasmas (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 3328-3336 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Analysis is presented of K- and 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 n=3-1 lines in H- and He-like Ar (Ar Ly-β and He-β, 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 into 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-β and its associated dielectronic satellites to theory is shown to provide a simultaneous measure of electron temperature and electron density. 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 Ne∼1025 cm−3 and is under continuing investigation. (Based on the invited paper 8I3 at the 1992 APS/DPP annual meeting [Bull. Am. Phys. Soc. 37, 1553 (1992)].)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860964
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Short wavelength x-ray laser research at the Lawrence Livermore National Laboratory (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 2326-2337 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Laboratory x-ray lasers are currently being studied by researchers worldwide. This paper reviews some of the recent work carried out at Lawrence Livermore National Laboratory. Laser action has been demonstrated at wavelengths as short as 35.6 A(ring) while saturation of the small signal gain has been observed with longer wavelength schemes. Some of the most successful schemes to date have been collisionally pumped x-ray lasers that use the thermal electron distribution within a laser-produced plasma to excite electrons from closed shells in neon- and nickel-like ions to metastable levels in the next shell. Attempts to quantify and improve the longitudinal and transverse coherence of collisionally pumped x-ray lasers are motivated by the desire to produce sources for specific applications. Toward this goal there is a large effort underway to enhance the power output of the Ni-like Ta x-ray laser at 44.83 A(ring) as a source for x-ray imaging of live cells. Improving the efficiency of x-ray lasers in order to produce saturated output with smaller pump lasers is also a goal of this work.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860203
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    8–11-keV x-ray sources for imaging and absorption experiments : Proceedings of the 9th topical conference on high temperature plasma diagnotics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 5104-5107 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have measured the 8–11-keV emission spectra from plasmas produced by impinging 0.53-μm, 100- and 200-ps FWHM Gaussian laser pulses on targets of different materials. The experimental spectra from W and Zn are identified by comparison with local thermodynamic equilibrium plasma emission calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143452
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Line broadening of Ne-like xenon as a diagnostic for high-density implosion experiments : Eighth topical conference on high−temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2780-2782 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The broadening of x-ray spectral lines has become an established diagnostic of Ne in high-density plasmas, particularly those of interest in inertial confinement fusion (ICF). Work to date has concentrated mostly on the broadening of K-shell lines in moderate Z (Z∼10–20) ions in plasmas with electron densities up to 1024 cm−3. In this paper we report on calculations of line broadening for Ne-like Xe (Xe44+) appropriate for diagnosis of higher density plasmas with Ne∼1025 cm−3. These calculations have been performed with a recently developed state of the art computer code which treats the ion and electron broadening in the quasi-static and impact approximations, respectively. In this paper, we summarize recent work examining the behavior of the width of the Ne-like Xe 3–2 and 4–2 transitions with electron density. The broadening of the 1s–3p line in H-like Ar and the 1s2–1s3p transition in He-like Ar is also studied in order to benchmark the code used in the calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141829
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    Paper (German National Licenses)
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