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  • 1995-1999  (19)
  • 1
    Electronic Resource
    Electronic Resource
    Self-consistent stability analysis of ablation fronts in inertial confinement fusion (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 2122-2128 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The linear stability analysis of accelerated ablation fronts is carried out self-consistently by retaining the effect of finite thermal conductivity. Its temperature dependence along with the density gradient scale length are adjusted to fit the density profiles obtained in the one-dimensional simulations. The effects of diffusive radiation transport are included through the nonlinear thermal conductivity (κ∼Tν). The growth rate is derived by using a boundary layer analysis for Fr(very-much-greater-than)1 (Fr is the Froude number) and a WKB approximation for Fr(very-much-less-than)1. The self-consistent Atwood number depends on the mode wavelength and the power law index for thermal conduction. The analytic growth rate and cutoff wave number are in good agreement with the numerical solutions for arbitrary ν(approximately-greater-than)1. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871664
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  • 2
    Electronic Resource
    Electronic Resource
    Direct-drive laser-fusion experiments with the OMEGA, 60-beam, 〉40 kJ, ultraviolet laser system (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 2108-2112 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: OMEGA, a 60-beam, 351 nm, Nd:glass laser with an on-target energy capability of more than 40 kJ, is a flexible facility that can be used for both direct- and indirect-drive targets and is designed to ultimately achieve irradiation uniformity of 1% on direct-drive capsules with shaped laser pulses (dynamic range (approximately-greater-than)400:1). The OMEGA program for the next five years includes plasma physics experiments to investigate laser–matter interaction physics at temperatures, densities, and scale lengths approaching those of direct-drive capsules designed for the 1.8 MJ National Ignition Facility (NIF); experiments to characterize and mitigate the deleterious effects of hydrodynamic instabilities; and implosion experiments with capsules that are hydrodynamically equivalent to high-gain, direct-drive capsules. Details are presented of the OMEGA direct-drive experimental program and initial data from direct-drive implosion experiments that have achieved the highest thermonuclear yield (1014 DT neutrons) and yield efficiency (1% of scientific breakeven) ever attained in laser-fusion experiments. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871662
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  • 3
    Electronic Resource
    Electronic Resource
    Self-consistent stability analysis of ablation fronts with small Froude numbers (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 4665-4676 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The linear growth rate of the Rayleigh–Taylor instability is calculated for accelerated ablation fronts with small Froude numbers (Fr(very-much-less-than)1). The derivation is carried out self-consistently by including the effects of finite thermal conductivity (κ∼Tν) and density gradient scale length (L). It is shown that long-wavelength modes with wave numbers kL0(very-much-less-than)1 [L0=νν/(ν+1)ν+1 min(L)] have a growth rate γ(approximately-equal-to)(square root of)ATkg−βkVa, where Va is the ablation velocity, g is the acceleration, AT=1+O[(kL0)1/ν], and 1〈β(ν)〈2. Short-wavelength modes are stabilized by ablative convection, finite density gradient, and thermal smoothing. The growth rate is γ=(square root of)αg/L0+c20k4L20V2a−c0k2L0Va for 1(very-much-less-than)kL0(very-much-less-than)Fr−1/3, and γ=c1g/(Vak2L20)−c2kVa for the wave numbers near the cutoff kc. The parameters α and c0−2 mainly depend on the power index ν; and the cutoff kc of the unstable spectrum occurs for kcL0∼Fr−1/3(very-much-greater-than)1. Furthermore, an asymptotic formula reproducing the growth rate at small and large Froude numbers is derived and compared with numerical results. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872078
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  • 4
    Electronic Resource
    Electronic Resource
    Self-consistent stability analysis of ablation fronts with large Froude numbers (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 1402-1414 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The linear stability analysis of accelerated ablation fronts is carried out self-consistently by retaining the effect of finite thermal conductivity. Its temperature dependence is included through a power law (κ∼Tν) with a power index ν(approximately-greater-than)1. The growth rate is derived for Fr(very-much-greater-than)1 (Fr is the Froude number) by using a boundary layer analysis. The self-consistent Atwood number and the ablative stabilization term depend on the mode wavelength, the density gradient scale length, and the power index ν. The analytic formula for the growth rate is shown to be in excellent agreement with the numerical fit of Takabe, Mima, Montierth, and Morse [Phys. Fluids 28, 3676 (1985)] for ν=2.5 and the numerical results of Kull [Phys. Fluids B 1, 170 (1989)] over a large range of ν's. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871730
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  • 5
    Electronic Resource
    Electronic Resource
    Nonlinear evolution of multimode Rayleigh–Taylor instability in two and three dimensions (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2465-2472 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nonlinear evolution of the Rayleigh–Taylor instability from multimode initial perturbations is studied by two complementary approaches. First, a statistical-mechanics bubble-merger model is presented, that enables determination of the late-time scaling properties based on single-mode and two-bubble interaction physics. The results for Rayleigh–Taylor (RT) and Richtmyer–Meshkov (RM) bubble and spike front penetrations are given, as well as scaling laws for mixing under a time-dependent driving acceleration. The second approach is a modal model, in which nonlinear mode coupling and saturation are included in an equation for effective modes that describe the mixed region. The importance of mode coupling in the generation of large structure that dominates the late stage evolution, and the relative importance of long-wavelength components in the initial perturbation spectra on the late-stage evolution are studied. Finally, multimode RT instability in three dimensions is studied by both full-scale simulations and the modal model. The effect and late-stage memory loss of different aspect ratios in the initial perturbation are demonstrated. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871476
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  • 6
    Electronic Resource
    Electronic Resource
    Growth rates of the ablative Rayleigh–Taylor instability in inertial confinement fusion (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 1446-1454 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A simple procedure is developed to determine the Froude number Fr, the effective power index for thermal conduction ν, the ablation-front thickness L0, the ablation velocity Va, and the acceleration g of laser-accelerated ablation fronts. These parameters are determined by fitting the density and pressure profiles obtained from one-dimensional numerical simulations with the analytic isobaric profiles of Kull and Anisimov [Phys. Fluids 29, 2067 (1986)]. These quantities are then used to calculate the growth rate of the ablative Rayleigh–Taylor instability using the theory developed by Goncharov et al. [Phys. Plasmas 3, 4665 (1996)]. The complicated expression of the growth rate (valid for arbitrary Froude numbers) derived by Goncharov et al. is simplified by using reasonably accurate fitting formulas. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872802
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  • 7
    Electronic Resource
    Electronic Resource
    Modal model for the nonlinear multimode Rayleigh–Taylor instability (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 3073-3090 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A modal model for the Rayleigh–Taylor (RT) instability, applicable at all stages of the flow, is introduced. The model includes a description of nonlinear low-order mode coupling, mode growth saturation, and post-saturation mode coupling. It is shown to significantly extend the range of applicability of a previous model proposed by Haan, to cases where nonlinear mode generation is important. Using the new modal model, we study the relative importance of mode coupling at late nonlinear stages and resolve the difference between cases in which mode generation assumes a dominant role, leading to the late time inverse cascade of modes and loss of memory of initial conditions, and cases where mode generation is not important and memory of initial conditions is retained. Effects of finite density ratios (Atwood number A〈1) are also included in the model and the difference between various measures of the mixing zone penetration depth for A〈1 is discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871655
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  • 8
    Electronic Resource
    Electronic Resource
    Self-consistent cutoff wave number of the ablative Rayleigh–Taylor instability (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 3844-3851 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The cutoff wave number of the ablative Rayleigh–Taylor instability is calculated self-consistently by including the effects of finite thermal conduction. The derived cutoff wave number is quite different from the one obtained with the incompressible fluid (∇⋅v˜=0) or sharp boundary models, and it is strongly dependent on thermal conductivity (K∼Tν) and the Froude number (Fr). The derivation is carried out for values of ν(approximately-greater-than)1, Fr(approximately-greater-than)1, and it is valid for some regimes of interest to direct and indirect-drive inertial confinement fusion (ICF). The analytic formula for the cutoff wave number is in excellent agreement with the numerical results of Kull [Phys. Fluids B 1, 170 (1989)]. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871083
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  • 9
    Electronic Resource
    Electronic Resource
    The upgrade to the OMEGA laser system : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 508-510 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The upgrade to the OMEGA laser system, a 30-kJ, 351-nm, 60-beam direct-drive laser-fusion system is reported here. The system configuration is presented along with the status of its construction and the plans for system activation. The system utilizes rod and disk amplifiers and frequency tripling to produce UV pulses which are smoothed using phase conversion and smoothing by spectral dispersion. Dual driver lines will feed the propagation of two co-axial beams, which have different pulse widths and occupy different portions of the laser aperture. The laser system will be completed in November 1994 and the target area in March 1995. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146333
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  • 10
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    Feedout and Rayleigh-Taylor Seeding Induced by Long Wavelength Perturbations in Accelerated Planar Foils (1998)
    American Physical Society
    Details
    Publication Date: 1998-12-21
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
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