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Detailed implosion modeling of deuterium-tritium layered experiments on the National Ignition Facilitya)
a)Paper BI3 1, Bull. Am. Phys. Soc. , 24 (2012).
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10.1063/1.4802194
/content/aip/journal/pop/20/5/10.1063/1.4802194
http://aip.metastore.ingenta.com/content/aip/journal/pop/20/5/10.1063/1.4802194

Figures

Image of FIG. 1.
FIG. 1.

Adjusted 1-D x-ray drive used in capsule-only simulations for shot N120205 (a) that was matched to the VISAR shock timing from shot N120108 (b) and ConA measured implosion trajectory from shot N120122 (c). In (b) and (c), the red curves show the simulated data from the 1-D adjusted implosions, and the black trace and black points, respectively, represent the experimental data. The insets show example raw data.

Image of FIG. 2.
FIG. 2.

Match to ConA observables from N120122 other than the implosion trajectory shown in Fig. 1(c) . Shown in panels (a)–(d) are shell mass averaged implosion velocity, shell remaining mass, peak shell density, and shell thickness. In each panel, the red curve shows the result of the 1-D adjusted simulation, and the black points with error bars show the data. Aside from the late time shell remaining mass (b) and early time shell thickness (d), the agreement is fairly close between experiment and the adjusted simulation.

Image of FIG. 3.
FIG. 3.

Example roughness power spectra used as hydrodynamic instability seeds in 2-D simulations for shot N120205. Panel (a) shows the ice roughness spectrum as a function of Legendre mode number measured from three views of the ice layer prior to shot (green, red, and blue curves). Also shown in black is the maximum allowed roughness according to ignition specifications. Panel (b) shows the outer ablator surface roughness as measured from eighteen meridian AFM traces and one equatorial trace. For comparison, the allowed roughness from the ignition specifications is also shown.

Image of FIG. 4.
FIG. 4.

Imploded configurations at bang time from three realizations of the post-shot simulation for N120205. The upper half of each panel shows the material density, and the lower half shows the material regions. Dark blue corresponds to the DT fuel, and the other colors to the various doped ablator layers. The red contour demarcates the hot spot boundary.

Image of FIG. 5.
FIG. 5.

Comparison of simulated and measured values for four principal experimental observables across the ensemble of post-shot simulations from 2012. Panels (a)–(d) show neutron down-scatter ratio (DSR), ion temperature inferred from the Doppler broadened primary neutron spectrum, hot spot size, and primary neutron yield as a function of shot number. In each panel, the data are represented by the black symbols with error bars, and the simulated results are the red symbols. The error bars on the simulation results are the RMS variation between different roughness realizations used in simulations. In most cases, these error bars are smaller than the symbol size. These simulation results do not include α-particle deposition.

Image of FIG. 6.
FIG. 6.

Comparison of simulated versus measured yield for the ensemble of shots simulated both with and without α-particle deposition included in the simulations. Panel (a) shows yield values versus shot number, and panel (b) shows the ratio of experimentally measured yield to 2-D simulation. The horizontal dashed lines in (b) give the average yield over simulated for the entire ensemble of shots.

Image of FIG. 7.
FIG. 7.

Dependence of simulated observables for shot N120321 on increased ablator surface roughness relative to measured. Increasing the surface roughness by a factor of five brings the simulations into approximate agreement with the observed neutron yield, ion temperature, and hot spot size. Shell break up at this high roughness, however, degrades the simulated DSR well below observation. These simulations include α-particle deposition.

Image of FIG. 8.
FIG. 8.

Dependence of simulated observables for shot N120321 on mass of pre-loaded ablator material mixed into the central DT gas. An injected mass of ∼1000 ng brings the simulated yield into agreement with observation but degrades the simulated ion temperature and hot spot size below the measured values. Radiative collapse in the hot spot for large mix masses increases the DSR well above the measurement. These simulations include α-particle deposition.

Image of FIG. 9.
FIG. 9.

3-D surface realizations in HYDRA for shot N120205. (a) shows the DT ice-gas interface including ice grooves, and (b) shows the ablator outer surface combining AFM and PSDI surface characterization. The color scales show the radial deviation in height along the surface.

Image of FIG. 10.
FIG. 10.

3-D simulation of N120205 at bang time. The cutaway green surface shows the fuel-ablator interface, and the enclosed red surface shows the 1 keV ion temperature isosurface, an effective indicator of the boundary between the low density hot spot and high density cold, compressed fuel. The large, spike-like deviations in the fuel-ablator interface correspond to large, localized defects on the initial ablator surface.

Image of FIG. 11.
FIG. 11.

2-D slice through the 3-D simulation in Fig. 10 aligned with the hohlraum axis (a). The color scale gives the density. The corresponding 2-D simulation result is shown in (b) on the same color scale. Larger Rayleigh-Taylor spikes penetrating the hot spot are apparent in the 3-D simulation than in 2-D as well as larger bubbles rising into the dense shell.

Image of FIG. 12.
FIG. 12.

2-D slice analogous to Fig. 11 showing flow speed in the hot spot. Nearly twice the peak flow velocity is reached in the 3-D simulation compared to 2-D representing implosion kinetic energy that is not effectively converted into fuel compression or hot spot heating. More fine-scale, turbulent-like features are also apparent in the 3-D result that are absent in the 2-D equivalent.

Tables

Generic image for table
Table I.

2012 NIF ignition experiments simulated in this study.

Generic image for table
Table II.

Simulated outputs for three different 2-D realizations of N120205.

Generic image for table
Table III.

Summary of simulated outputs for N120205: 1-D, 2-D, and 3-D.

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2013-05-31
2014-04-16
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Detailed implosion modeling of deuterium-tritium layered experiments on the National Ignition Facilitya)
http://aip.metastore.ingenta.com/content/aip/journal/pop/20/5/10.1063/1.4802194
10.1063/1.4802194
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