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  • 1
    Electronic Resource
    Electronic Resource
    Growth of pellet imperfections and laser imprint in direct drive inertial confinement fusion targets : The 42nd annual meeting of the division of plasma physics of the American Physical Society and the 10th international congress on plasma physics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 2287-2295 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Simple hydrodynamic models for describing the Richtmyer–Meshkov (RM) growth and the Rayleigh–Taylor (RT) instability are tested by simulation. The RM sharp boundary model predictions are compared with numerical simulations of targets with surface perturbations or stationary intensity perturbations. Agreement is found in the overall trends, but the specific behavior can be significantly different. RM growth of imprint from optically smoothed lasers is also simulated and quantified. The results are used to calculate surface perturbations, growth factors, and laser imprint efficiencies. These in turn are used with standard RT growth formulas to predict perturbation growth in multimode simulations of compression and acceleration of planar and spherical targets. The largest differences between prediction and theory occur during ramp-up of the laser intensity, where RT formulas predict more growth than seen in the simulations. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1360709
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  • 2
    Electronic Resource
    Electronic Resource
    The Nike KrF laser facility: Performance and initial target experiments (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 2098-2107 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Krypton-fluoride (KrF) lasers are of interest to laser fusion because they have both the large bandwidth capability ((approximately-greater-than)THz) desired for rapid beam smoothing and the short laser wavelength (1/4 μm) needed for good laser–target coupling. Nike is a recently completed 56-beam KrF laser and target facility at the Naval Research Laboratory. Because of its bandwidth of 1 THz FWHM (full width at half-maximum), Nike produces more uniform focal distributions than any other high-energy ultraviolet laser. Nike was designed to study the hydrodynamic instability of ablatively accelerated planar targets. First results show that Nike has spatially uniform ablation pressures (Δp/p〈2%). Targets have been accelerated for distances sufficient to study hydrodynamic instability while maintaining good planarity. In this review we present the performance of the Nike laser in producing uniform illumination, and its performance in correspondingly uniform acceleration of targets. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871661
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  • 3
    Electronic Resource
    Electronic Resource
    TRIHYDROXY-METHYL-ANTHRAQUINONES. II (1923)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 45 (1923), S. 2455-2462 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja01663a030
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  • 4
    Electronic Resource
    Electronic Resource
    Inverse cascades in two-dimensional compressible turbulence. I. Incompressible forcing at low Mach number (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 1481-1486 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A fundamental property of forced, dissipative, two-dimensional incompressible Navier–Stokes (NS) systems is the dominance at long times of the longest wavelengths available to the flow. This dominance, attributed to an inverse cascade of energy with respect to enstrophy [Kraichnan, Phys. Fluids 10, 1417 (1967)], has been observed in spectrally accurate numerical simulations (see Refs. 5–7) of the incompressible NS equations. The numerical investigation of this behavior is extended to the weakly compressible regime by means of the fully compressible Fourier collocation code combox with a solenoidal forcing function that imparts no net momentum and stirs the fluid in a wave-number band in the neighborhood of kf=11. A comparison of spectral results from combox simulations with an average Mach number of 0.22 with those from identically forced incompressible simulations, at Reynolds numbers ≤700, indicates (1) the compressible and incompressible wave-number dependences in both the energy cascading and enstrophy cascading regions are nearly identical; (2) in the compressible calculation, a dual power law is also observed in density and pressure fluctuations; and (3) continued (kf=11) forcing leads to overall continued growth in the longest accessible velocity field wavelength, in both the incompressible and compressible cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857597
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  • 5
    Electronic Resource
    Electronic Resource
    The effect of shape in the three-dimensional ablative Rayleigh–Taylor instability. I: Single-mode perturbations (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 571-584 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nonlinear saturation amplitudes attained by Rayleigh–Taylor perturbations growing on ablatively stabilized laser fusion targets are crucial in determining the survival time of those targets. For a given set of baseline simulation parameters, the peak amplitude is found to be a progressive function of cross-sectional perturbation shape as well as of wave number, with three-dimensional (3-D) square modes and two-dimensional (2-D) axisymmetric bubbles saturating later, and at higher amplitudes than two-dimensional planar modes. In late nonlinear times hydrodynamic evolution diverges; the 3-D square mode bubble continues to widen, while the 2-D axisymmetric bubble fills in.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860543
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  • 6
    Electronic Resource
    Electronic Resource
    Evidence in the second-harmonic emission for self-focusing of a laser pulse in a plasma (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 2563-2569 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Short-pulse (300 psec), high-intensity (1014−1015 W/cm2) Nd-laser light was propagated into variable scale length plasmas (Ln≡n/∇n=200–400 μm at 0.1 critical density) preformed by long-pulse (4 nsec), low-intensity ((approximately-equal-to)6×1012 W/cm2) irradiation of planar targets. For high short-pulse intensities (≥5×1014 W/cm2), time-integrated images show filament-shaped regions of second-harmonic (2ω0) emission from the low density (0.01≤ne/nc≤0.2) region of the ablation plasma. Two-dimensional computer calculations of the hyrodynamics and laser beam propagation indicate that these filaments are consistent with ponderomotive self-focusing of the short pulse. A theoretical model that explains the 2ω0 generation mechanism within low-density filaments is also presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865264
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  • 7
    Electronic Resource
    Electronic Resource
    Hydrodynamic target response to an induced spatial incoherence-smoothed laser beam (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 2640-2651 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: One of the critical elements for high-gain target designs is the high degree of symmetry that must be maintained in the implosion process. The induced spatial incoherence (ISI) concept has some promise for reducing ablation pressure nonuniformities to ≈1%. The ISI method produces a spatial irradiance profile that undergoes large random fluctuations on picosecond time scales but is smooth on long time scales. The ability of the ISI method to produce a nearly uniform ablation pressure is contingent on both temporal smoothing and thermal diffusion. In the start-up phase of a shaped reactorlike laser pulse, the target is directly illuminated by the laser light and thermal diffusion is not effective at smoothing residual nonuniformities in the laser beam. During this period in the laser pulse, the target response is dominated by the initial shock generated by the laser pulse and the results indicate that this first shock can be the determining factor in the success or failure of the implosion process. The results of numerical simulations of several target/laser pulse designs which were investigated in an attempt to mitigate the impact of the initial shock structure stemming from the early temporal phase of an ISI-smoothed laser beam are presented. It is shown that "foamlike'' layers, multiple laser wavelengths, and shallow angles of incidence can sharply reduce the perturbation level stemming from the first shock.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859976
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  • 8
    Electronic Resource
    Electronic Resource
    Simulation of the Rayleigh–Taylor instability in colliding, ablatively driven laser foils (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 3485-3493 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper reports results from a series of numerical simulations of a pair of independently accelerated rectilinear foils in the presence of the ablative Rayleigh–Taylor (RT) instability on the laser-side surfaces. The foil thickness and laser intensity are chosen to be in the range relevant to high-gain inertial fusion pellets, with 80 μm thick plastic (CH) foils accelerated toward each other from a separation distance of 650 μm by a 1/4 μm laser beam with an intensity of 3×1014 W/cm2. At early times the foils are physically well separated from one another, and evolve independently in a way that is fully consistent with the previously studied evolution of ablatively RT unstable planar targets [Gardner et al., Phys. Fluids B 3, 1070 (1991)]. Subsequently, pressure builds up in the region between the foils, causing them to decelerate. This stabilizes the RT growth on the laser sides, while driving the RT instability on the inner sides. For thin foils, laser-side RT bubbles become rapidly growing inner surface RT spikes which mix and coalesce as the foils are pressed together.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859726
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  • 9
    Electronic Resource
    Electronic Resource
    Laser interaction in long-scale-length plasmas (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 1305-1320 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Absorption of a short-pulse, high-intensity Nd-laser beam (vacuum irradiance of 1014 to 1015 W/cm2) by preformed plasmas of different density scale lengths is investigated. Increased effects of plasma instabilities are found at longer scale lengths. The amount of backscattered light increases with plasma scale length and limits the absorption fraction at the longest scale length. The onset of suprathermal electron production, deduced from observations of energetic (20 to 50 keV) x rays, occurs at lower laser irradiance for longer-scale-length plasmas. A correlation between energetic x rays and 3ω0/2 emission suggests that the suprathermal electrons are produced by a plasma instability at quarter-critical density. At higher intensities there is evidence for severe perturbations of the preformed plasma and for self-focusing of the incident beam.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865880
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