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  • 1
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Execution and modeling of drive symmetry experiments in gas-filled hohlraums have been pursued to provide both a better understanding of radiation symmetry in such hohlraums and to verify the accuracy of the design tools which are used to predict target performance for the National Ignition Facility (NIF) [J. Lindl, Phys. Plasmas 2, 3933 (1995)]. In this paper, the results of a series of drive symmetry experiments using gas-filled hohlraums at the Nova laser facility [C. Bibeau et al., Appl. Opt. 31, 5799 (1992)] at Lawrence Livermore National Laboratory are presented. A very important element of these experiments was the use of kineform phase plates (KPP) to smooth the Nova beams. The effect of smoothing the ten Nova beams with KPP phase plates is to remove most of the beam bending which had been observed previously, leaving a residual bending of only 1.5°, equivalent to a 35 μm pointing offset at the hohlraum wall. The results show that the symmetry variation with pointing of implosions in gas-filled hohlraums is consistent with time integrated modeling. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Understanding drive symmetry in gas-filled hohlraums is currently of interest because the baseline design of the indirect drive ignition target for the planned National Ignition Facility uses a gas-filled hohlraum. This paper reports on the results of a series of experiments performed at the Nova laser [C. Bibeau et al. Appl. Opt. 31, 5799 (1992)] facility at Lawrence Livermore National Laboratory with the goal of understanding time-dependent drive symmetry in gas filled hohlraums. Time-dependent symmetry data from capsule implosions and reemission targets in gas-filled hohlraums are discussed. Results of symmetry measurements using thin wall gas-filled hohlraums are also discussed. The results show that the gas is effective in impeding the motion of the wall blowoff material, and that the resulting implosion performance of the capsule is not significantly degraded from vacuum results. The implosion symmetry in gas differs from vacuum results with similar laser pointing indicating a shift in beam position on the hohlraum wall and hotter drive at the capsule's poles than at the equator. A theory has been proposed to explain the observed shift as a plasma physics effect: beam steering due to filamentation and transverse plasma flows. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 3747-3752 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A CO2 laser was used to irradiate hollow polystyrene cylinders along their axis. The laser-generated high-energy electrons appear to uniformly heat the cylinder throughout its volume and the cylinder explodes. The imploding and stagnation character of the exploding cylinder gives rise to a long x-ray pulse, much longer than the laser pulse, and to a peak emission that occurs after the laser pulse. The fast ions that are generated appear not to interact with the thermal plasma. Two-dimensional calculations that reproduce much of the experimental x-ray signature and observed hydrodynamic flow are presented.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 55 (1977), S. 211-240 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Electron streams with type III burst characteristics are numerically modeled. The electronplasma wave quasilinear interaction is assumed to be the dominant velocity diffusion process. The quasilinear equations with the addition of spontaneous emission, magnetic and collisional effects are numerically solved as an initial value and a half-space boundary value problem with time, distance and velocity as the independent variables for a solar-type background plasma and a type-III-like stream. Background density and temperature coordinate structure, spontaneous emission, magnetic fields, electron-ion collisions, stream reabsorption and wave pileup are shown to affect propagation and are incorporated into a physical description of the stream motion. The calculated electron flux-time profiles at the Earth suggest scatter-free propagation and compare well with type III stream observations.
    Type of Medium: Electronic Resource
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