High-mode Rayleigh-Taylor growth in NIF ignition capsules

Hammel, B. A.; Haan, S. W.; Clark, Daniel; Edwards, M. J.; Langer, Steven H.; Marinak, M. M.; Patel, Mehul V.; Salmonson, J. D.; Scott, H. A.

doi:10.1016/j.hedp.2009.12.005

Cited by 162 publications

(79 citation statements)

References 11 publications

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“…It gives equation of state and selfdiffusion coefficients with an accuracy comparable to ab-initio simulations but is computationally much more efficient. The challenge of accurately modeling dense plasmas over a wide range of conditions represents an unsolved problem lying at the heart of many important phenomena such as inertial confinement fusion [1], exoplanets and white dwarfs [2,3]. The production of large scale and accurate tabulations of data such as equation of state and transport coefficients as a function of density and temperature is a formidable task, requiring a consistent quantum mechanical treatment of the many-electron problem together with a classical treatment of the nuclear motion.…”

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confidence: 99%

Pseudoatom molecular dynamics

2015

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A new approach to simulating warm and hot dense matter that combines density functional theory based calculations of the electronic structure to classical molecular dynamics simulations with pair interaction potentials is presented. The new method, which we call pseudoatom molecular dynamics (PAMD), can be applied to single or multi-component plasmas. It gives equation of state and selfdiffusion coefficients with an accuracy comparable to ab-initio simulations but is computationally much more efficient.PACS numbers: 51.20.+d, 51.30.+i, 52.25.Kn, 52.65.Yy The challenge of accurately modeling dense plasmas over a wide range of conditions represents an unsolved problem lying at the heart of many important phenomena such as inertial confinement fusion [1], exoplanets and white dwarfs [2,3]. The production of large scale and accurate tabulations of data such as equation of state and transport coefficients as a function of density and temperature is a formidable task, requiring a consistent quantum mechanical treatment of the many-electron problem together with a classical treatment of the nuclear motion. The atoms in the plasma may have bound states or be fully ionized, the electrons may be fully degenerate or approaching their classical limit. The nuclear fluid can range from weakly through to strongly coupled. A consistent, reliable and accurate treatment across all these physical regimes with an approach that remains computationally tractable remains as an open problem.Plasmas of interest are typically one to thousands of times solid density, and have temperatures from about 1eV (∼10kK) to thousands of eV. The difficulty of creating and controlling such plasmas in the laboratory explains the lack of experimental data to guide theoretical development, though ongoing campaigns at National Ignition Facility [4] and elsewhere (eg.[5]), and recent advances in X-ray scattering techniques [6] are beginning to shed light on this problem.From a simulations perspective, powerful and complex tools exist that can provide benchmark calculations. In the lower temperature regime (a few eV) one such tool is Kohn-Sham (KS) density functional theory molecular dynamics (DFT-MD) (eg. [7]). Electrons are treated quantum mechanically through KS-DFT and ions are propagated with classical MD. The simulations are very computationally expensive and this cost scales poorly with temperature, limiting the method to lower temperatures. In practice KS-DFT-MD also relies on a pseudopotential approximation, which reduces the computational overhead by limiting the number of actively modeled electrons, through an ad hoc modification of the electron- (r), n ext e (r) and n P A e (r), as described in the text. Also shown is the bound state (or ion) contribution (n ion e (r)) to n P A e (r) and the valence electron contribution n scr e (r). The double peak structure in n ion e (r) reflects the bound state shell structure in the aluminum ion, while the oscillations in the valence contribution n scr e (r) are the well known Friedel oscillations, whic...

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confidence: 99%

Pseudoatom molecular dynamics

2015

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“…To model these extremely fine-scale features, specialized high-resolution 2D simulations must be run [22]. To include the important effects of the tent and the fill tube in nominal resolution simulations, surrogate perturbations are then derived from these high-resolution simulations, and their longer-wavelength features can then be initialized in the lower resolution cases.…”

Section: Discussionmentioning

confidence: 99%

“…As shown in figure 1, the linear stability of these implosions is quantified by comparing their ablation front growth factors. These growth factors are defined as the ratio of the perturbation amplitude at the time of peak implosion velocity relative to the initial perturbation amplitude for an individual Legendre mode [21][22][23]. For all cases, the simulations were run using a 2D wedge initialized with a small Gaussian bump (15 μm wide by 1 nm in height) on the ablator surface at the axis of symmetry.…”

Section: Linear Stability Simulationsmentioning

confidence: 99%

“…In progressing from N130812 to N140819, the maximum ablation front growth factor more than doubles from ∼170 to ∼430. Also evident in these spectra is the importance of the ablative Richtmyer-Meshkov (RM) oscillation [25] in setting the node in the growth factor spectrum [22,23,[26][27][28][29][30]: as the ablator was thinned in N140520 and N140819, and the pulse length consequently shortened, the time for this RM oscillation was reduced and the location of the growth factor node moved froml 80 to ∼120, resulting in enhanced growth of shorter wavelength features. Figure 2 plots the maximum of each growth factor spectrum from figure 1 versus simulated peak implosion velocity.…”

Section: Linear Stability Simulationsmentioning

confidence: 99%

“…It has been speculated that mixing of hot ablator material into the DT fuel [22,58] or direct pre-heating of the fuel by energetic electrons generated from laser-plasma interactions in the hohlraum [13,59,60] could raise the effective adiabat of the fuel and reduce its compressibility, thereby explaining the apparent Figure 9. Renderings of the imploded hot spots for the four 3D high foot simulations at their respective bang times.…”

Section: Simulations Including Hot Electron Pre-heatmentioning

confidence: 99%

See 2 more Smart Citations

Capsule modeling of high foot implosion experiments on the National Ignition Facility

Clark

Kritcher

Milovich

et al. 2017

Plasma Phys. Control. Fusion

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This paper summarizes the results of detailed, capsule-only simulations of a set of high foot implosion experiments conducted on the National Ignition Facility (NIF). These experiments span a range of ablator thicknesses, laser powers, and laser energies, and modeling these experiments as a set is important to assess whether the simulation model can reproduce the trends seen experimentally as the implosion parameters were varied. Two-dimensional (2D) simulations have been run including a number of effects-both nominal and off-nominal-such as hohlraum radiation asymmetries, surface roughness, the capsule support tent, and hot electron pre-heat. Selected three-dimensional simulations have also been run to assess the validity of the 2D axisymmetric approximation. As a composite, these simulations represent the current state of understanding of NIF high foot implosion performance using the best and most detailed computational model available. While the most detailed simulations show approximate agreement with the experimental data, it is evident that the model remains incomplete and further refinements are needed. Nevertheless, avenues for improved performance are clearly indicated.

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Lenard‐Balescu Calculations and Classical Molecular Dynamics Simulations of Electrical and Thermal Conductivities of Hydrogen Plasmas

Whitley

Scullard

Benedict

et al. 2014

Contrib. Plasma Phys.

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We present a discussion of kinetic theory treatments of linear electrical and thermal transport in hydrogen plasmas, for a regime of interest to inertial confinement fusion applications. In order to assess the accuracy of one of the more involved of these approaches, classical Lenard-Balescu theory, we perform classical molecular dynamics simulations of hydrogen plasmas using 2-body quantum statistical potentials and compute both electrical and thermal conductivity from our particle trajectories using the Kubo approach. Our classical Lenard-Balescu results employing the identical statistical potentials agree well with the simulations. Comparison between quantum Lenard-Balescu and classical Lenard-Balescu for conductivities then allows us to both validate and critique the use of various statistical potentials for the prediction of plasma transport properties. These findings complement our earlier MD/kinetic theory work on temperature equilibration [1], and reach similar conclusions as to which forms of statistical potentials best reproduce true quantum behavior.

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High-mode Rayleigh-Taylor growth in NIF ignition capsules

Cited by 162 publications

References 11 publications

Pseudoatom molecular dynamics

Pseudoatom molecular dynamics

Capsule modeling of high foot implosion experiments on the National Ignition Facility

Lenard‐Balescu Calculations and Classical Molecular Dynamics Simulations of Electrical and Thermal Conductivities of Hydrogen Plasmas

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