Variable convergence liquid layer implosions on the National Ignition Facility

Zylstra, A. B.; Yi, Sunghwan; Haines, Brian; Olson, R. E.; Leeper, R. J.; Braun, Tom; Biener, Juergen; Kline, J. L.; Batha, S. H.; Hopkins, L. Berzak; Bhandarkar, S. D.; Bradley, P. A.; Crippen, J. W.; Farrell, M.; Fittinghoff, D. N.; Herrmann, H. W.; Huang, H.; Khan, S. F.; Kong, C.; Kozioziemski, B.; Kyrala, G. A.; Ma, T.; Meezan, N. B.; Merrill, F. E.; Nikroo, A.; Peterson, R. R.; Rice, N.; Sater, J.; Shah, Rahul; Stadermann, Michael; Volegov, P. L.; Walters, C. F.; Wilson, D. C.

doi:10.1063/1.5016349

Cited by 16 publications

(10 citation statements)

References 46 publications

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“…However, experiments operating at lower convergence ratios have observed significant reduction in hydrodynamic instabilities, and performance that is much closer to one-dimensional (this is discussed in more detail in § 2 b). This paper follows work by Olson et al [ 5 ] and Zylstra et al [ 6 ], who observed this on three NIF shots in the 12 < CR < 19 range. It was found that experiments operating at lower CR values in this range show good agreement with simulations, suggesting a region of phase space which is well described by current codes and where instabilities are of low significance.…”

Section: Introductionsupporting

confidence: 77%

“…The ability to well describe this shot with a 1D code suggests performance that is close to one-dimensional. Zylstra et al later analysed three liquid layer shots (including N160421) [6]. The three shots, with CR of 12, 17 and 19 (calculated using the same definition given in equation (1.1)) were compared with 2D simulations performed using the codes HYDRA and XRAGE.…”

Section: (B) Low Convergence Ratiomentioning

confidence: 99%

“…There is therefore a compromise to be made between improved idealized 1D performance, and increased agreement between simulation and experiment. Based on the results in [ 5 , 6 ], this work will use an upper limit of 16 for the convergence ratio (the first criterion which all simulations in the simulation campaign are tested against). This sits firmly in the region where the agreement is reasonably good, but enables a much greater level of 1D performance than would be possible using the lowest CR values in this range.…”

Section: Background and Theorymentioning

confidence: 99%

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One-dimensional hydrodynamic simulations of low convergence ratio direct-drive inertial confinement fusion implosions

Paddock

Martin

Ruskov

et al. 2020

Phil. Trans. R. Soc. A.

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Indirect drive inertial confinement fusion experiments with convergence ratios below 17 have been previously shown to be less susceptible to Rayleigh–Taylor hydrodynamic instabilities, making this regime highly interesting for fusion science. Additional limitations imposed on the implosion velocity, in-flight aspect ratio and applied laser power aim to further reduce instability growth, resulting in a new regime where performance can be well represented by one-dimensional (1D) hydrodynamic simulations. A simulation campaign was performed using the 1D radiation-hydrodynamics code HYADES to investigate the performance that could be achieved using direct-drive implosions of liquid layer capsules, over a range of relevant energies. Results include potential gains of 0.19 on LMJ-scale systems and 0.75 on NIF-scale systems, and a reactor-level gain of 54 for an 8.5 MJ implosion. While the use of 1D simulations limits the accuracy of these results, they indicate a sufficiently high level of performance to warrant further investigations and verification of this new low-instability regime. This potentially suggests an attractive new approach to fusion energy. This article is part of a discussion meeting issue ‘Prospects for high gain inertial fusion energy (part 2)’.

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Section: Introductionsupporting

confidence: 77%

Section: (B) Low Convergence Ratiomentioning

confidence: 99%

Section: Background and Theorymentioning

confidence: 99%

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One-dimensional hydrodynamic simulations of low convergence ratio direct-drive inertial confinement fusion implosions

Paddock

Martin

Ruskov

et al. 2020

Phil. Trans. R. Soc. A.

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“…Simulations predict that as the CR is increased, the hot spot gas is formed by increasing amounts of DT and carbon from the foam matrix. At high CR (≈20), about half of the hot spot mass is from the liquid and foam [106]. Data collected from these experiments, however, show no increase in mass and the hot spot is still formed entirely from the original DT vapor, Figure 15.…”

Section: Wetted Foam Capsulesmentioning

confidence: 93%

“…Then, a convergence-ratio scan (CR) was made with DT fuel. The CR was varied from 12 to 20 by simply varying the temperature of the capsule that varied the vapor pressure and hence gas mass in the core [104][105][106]. Onedimensional xRAGE [5] simulations were able to match the increasing yield as the CR was increased with a yield-over-simulated (YOS) of better than 0.8.…”

Section: Wetted Foam Capsulesmentioning

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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Pathways towards break even for low convergence ratio direct-drive inertial confinement fusion

et al. 2022

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Following indirect-drive experiments which demonstrated promising performance for low convergence ratios (below 17), previous direct-drive simulations identified a fusion-relevant regime which is expected to be robust to hydrodynamic instability growth. This paper expands these results with simulated implosions at lower energies of 100 and 270 kJ, and ‘hydrodynamic equivalent’ capsules which demonstrate comparable convergence ratio, implosion velocity and in-flight aspect ratio without the need for cryogenic cooling, which would allow the assumptions of one-dimensional-like performance to be tested on current facilities. A range of techniques to improve performance within this regime are then investigated, including the use of two-colour and deep ultraviolet laser pulses. Finally, further simulations demonstrate that the deposition of electron energy into the hotspot of a low convergence ratio implosion through auxiliary heating also leads to significant increases in yield. Results include break even for 1.1 MJ of total energy input (including an estimated 370 kJ of short-pulse laser energy to produce electron beams for the auxiliary heating), but are found to be highly dependent upon the efficiency with which electron beams can be created and transported to the hotspot to drive the heating mechanism.

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Variable convergence liquid layer implosions on the National Ignition Facility

Cited by 16 publications

References 46 publications

One-dimensional hydrodynamic simulations of low convergence ratio direct-drive inertial confinement fusion implosions

One-dimensional hydrodynamic simulations of low convergence ratio direct-drive inertial confinement fusion implosions

Effect of Impurity Atoms on Thermonuclear Yield

Pathways towards break even for low convergence ratio direct-drive inertial confinement fusion

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