Using a 2-shock 1D platform at NIF to measure the effect of convergence on mix and symmetry

Kyrala, G. A.; Pino, Jesse; Khan, S. F.; MacLaren, S. A.; Salmonson, J. D.; Ma, T.; Massé, L.; Tipton, Robert; Bradley, P. A.; Rygg, J. R.; Field, J. E.; Tommasini, R.; Ralph, J. E.; Turnbull, D.; Mackinnon, A. J.; Benedetti, L. R.; Bradley, D. K.; Nagel, S. R.; Celliers, P. M.; Dewald, E. L.; Dittrich, Thomas; Hopkins, L. Berzak; Izumi, N.; Kervin, M. L.; Kline, J. L.; Yeamans, C. B.; Hatarik, R.; Sayre, D. B.; Hartouni, E. P.; Pak, A.; Chen, K. C.; Hoover, D.

doi:10.1063/1.5038570

Cited by 7 publications

(1 citation statement)

References 40 publications

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“…The success of this campaign is demonstrated by the high ratio of measured-tocalculated clean yield (YOC) is shown in Figure 13. Because of its good symmetry, predictability, and large mass remaining to isolate the inner surface from outersurface mix, the 2-Shock platform was chosen for a study of the effect of convergence on inner-surface mixing into the DT fuel [98]. Up to 13 atm of tritium gas was imploded by a capsule that had its inner 2.5 µm of CH replaced by CD.…”

Section: The 2-shock Platformmentioning

confidence: 99%

Effect of Impurity Atoms on Thermonuclear Yield

Batha

2020

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The presence of impurity atoms in an inertial confinement fusion (ICF) implosion can greatly affect the burning of the thermonuclear fuel. This is a serious concern for attaining ignition as high atomic number atoms, such as carbon, can mix into the hot spot and reach the deuterium-tritium (DT) fuel, absorb energy from the implosion, and radiate away that energy. The temperature of the DT fuel drops and reduces the reactivity of the fuel resulting in lower thermonuclear yield. Fuel impurities can also be a useful diagnostic as when higher-Z atoms, such as Ar, Kr, and Xe, are purposefully mixed into the fuel. From the spectra emitted by these atoms, the temperature and density of the fuel can be deduced. The long history of using such tracer atoms by the national ICF program shows the great advances in experimental technique, diagnostic instruments, and atomic-physics modeling over the past 50 years. A particular set of experiments, the "High-Z" campaign, is reviewed in depth as this was the most systematic study of tracer element composition and quantity ever reported. Difficulties in interpreting the results of those experiments due to the limited code capabilities at that time are discussed. A main concern for the High-Z campaign was the then current state of non-Local Thermodynamic Equilibrium (nLTE) atomic physics models. The present state of nLTE modeling and its implementation in Los Alamos's multi-physics codes is discussed in this report. To further the understanding of the complex interaction of high-Z atoms in the gas, a survey of relevant existing experimental platforms at the National Ignition Facility (NIF) and the Omega Laser Facility are presented along with the current state of pertinent diagnostics at NIF and Omega. This review concludes with a discussion of the trade-off available between temperature and volume of the imploded ICF capsule with the goal of maximizing the total yield. 10 24 cm•3 3 x 10 23 cm•3

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Section: The 2-shock Platformmentioning

confidence: 99%

Effect of Impurity Atoms on Thermonuclear Yield

Batha

2020

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A simulation-based model for understanding the time dependent x-ray drive asymmetries and error bars in indirectly driven implosions on the National Ignition Facility

et al. 2019

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Time-dependent low-mode asymmetries are believed to play a leading role in limiting the performance of current inertial confinement fusion implosions on the National Ignition Facility (NIF) [E. I. Moses et al., Phys. Plasmas 16, 041006 (2009)]. These long wavelength modes are initiated and driven by asymmetries in the x-ray flux from the hohlraum; however, the underlying hydrodynamics of the implosion also act to modify and amplify these asymmetries. We present here a simulation-based model connecting the time-dependent drive asymmetry seen by the capsule to the measured inflight and hot spot symmetries. This approach is based on a Green's function analysis for which we evaluate the response of the capsule to impulses of drive asymmetry at a series of times. Our model sheds new light on the sensitivity to the drive asymmetry of an imploded capsule, giving a new tool for design. Inverting the problem and finding the drive asymmetry needed to match the experimental data allow us to tightly constrain the drive asymmetry seen by the capsule, providing an error estimate on the result. Doing so, we are able to point out when and how the complex hohlraum simulations start to deviate from what they should obtain to match the experimental data. Ultimately, we project to use this model to make some experimental recommendations to fix the time-dependent low-mode asymmetry of indirectly driven implosions and identify additional measurements to further constrain the asymmetries with a view to improving target design on the NIF.

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Pushered single shell implosions for mix and radiation trapping studies using high-Z layers on National Ignition Facility

et al. 2019

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Pushered Single Shells (PSSs) are an alternative approach to Inertial Confinement Fusion implosions that employ high-Z materials in the innermost capsule layer (pusher) as a means to enhance radiation trapping and lower core ignition requirements. However, adding high-Z materials can also increase losses due to mix, provide extra tamping, and make the capsule emission opaque to x-ray diagnostics. The first PSS implosions performed on the National Ignition Facility use plastic ablators with a germanium (Ge) dopant as a high-Z surrogate in the pusher to isolate the effects of high-Z mix and radiation trapping without changing tamping. Using a 2-shock laser pulse, the PSS implosions are designed and symmetrized to reach 3.7 keV core temperatures. A low concentration (2.8%) Ge dopant is added to the innermost layer, and the resulting effects on mix and x-ray opacity are observed. The method of separated reactants is used to infer information about mixing between the deuterated plastic pusher and the capsule fill gas (25% tritium) from the resulting nuclear DT reactions. Radiation transport is studied via capsule emission x-ray spectroscopy and imaging. Both nuclear and x-ray data corroborate the hypothesis that the addition of Ge strongly affects the mix region through radiation losses but has a minimal effect on the core and the warm, unmixed regions. Simulations using diffusive and turbulent mix models agree qualitatively with data, but quantitative agreement may require hybrid mix models that can model the transitional regime between turbulence and diffusion. Simulations matching the observables show increased core radiation trapping when Ge is added.

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Using a 2-shock 1D platform at NIF to measure the effect of convergence on mix and symmetry

Cited by 7 publications

References 40 publications

Effect of Impurity Atoms on Thermonuclear Yield

Effect of Impurity Atoms on Thermonuclear Yield

A simulation-based model for understanding the time dependent x-ray drive asymmetries and error bars in indirectly driven implosions on the National Ignition Facility

Pushered single shell implosions for mix and radiation trapping studies using high-Z layers on National Ignition Facility

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