Performance of High-Convergence, Layered DT Implosions with Extended-Duration Pulses at the National Ignition Facility

Smalyuk, V. A.; Atherton, L. J.; Benedetti, L. R.; Bionta, R. M.; Bleuel, D. L.; Bond, E.; Bradley, D. K.; Caggiano, J. A.; Callahan, D. A.; Casey, D. T.; Celliers, P. M.; Cerjan, C.; Clark, Dan; Dewald, E. L.; Dixit, S.; Döppner, T.; Edgell, D. H.; Edwards, M. J.; Frenje, J. A.; Johnson, M. Gatu; Glebov, V. Yu.; Glenn, S.; Glenzer, S. H.; Grim, G.; Haan, S. W.; Hammel, B. A.; Hartouni, E. P.; Hatarik, R.; Hatchett, S.; Hicks, D. G.; Hsing, W. W.; Izumi, N.; Jones, O. S.; Key, M. H.; Khan, S. F.; Kilkenny, J. D.; Kline, J. L.; Knauer, J. P.; Kyrala, G. A.; Landen, O. L.; Pape, S. Le; Lindl, J. D.; Ma, T.; MacGowan, B. J.; Mackinnon, A. J.; MacPhee, A. G.; McNaney, J. M.; Meezan, N. B.; Moody, J. D.; Moore, A. S.; Moran, M. J.; Moses, E. I.; Pak, A.; Parham, T.; Park, H.-S.; Patel, P. K.; Petrasso, R. D.; Ralph, J. E.; Regan, S. P.; Remington, B. A.; Robey, H. F.; Ross, J. S.; Spears, B. K.; Springer, P. T.; Suter, L. J.; Tommasini, R.; Town, R. P. J.; Weber, S. V.; Widmann, K.

doi:10.1103/physrevlett.111.215001

Cited by 49 publications

(18 citation statements)

References 32 publications

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“…40 In recent high-compression experiments on NIF, high fuel areal densities (up to $1.3 g/cm 2 ) have been achieved with fuel velocities of $320-330 km/s. 39,41 These key performance parameters were close to the goal of the ignition design, while the neutron yields were reduced by hydrodynamic instabilities and drive asymmetries. 39,41 The presence of mixed ablator material was also correlated with reduced experimental yields and temperatures in high-compression layered DT implosions.…”

Section: Introductionmentioning

confidence: 85%

Hydrodynamic instability growth and mix experiments at the National Ignition Facility

et al. 2014

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Hydrodynamic instability growth and its effects on implosion performance were studied at the National Ignition Facility [G. H. Miller, E. I. Moses, and C. R. Wuest, Opt. Eng. 443, 2841 (2004)]. Implosion performance and mix have been measured at peak compression using plastic shells filled with tritium gas and containing embedded localized carbon-deuterium diagnostic layers in various locations in the ablator. Neutron yield and ion temperature of the deuterium-tritium fusion reactions were used as a measure of shell-gas mix, while neutron yield of the tritium-tritium fusion reaction was used as a measure of implosion performance. The results have indicated that the low-mode hydrodynamic instabilities due to surface roughness were the primary culprits for yield degradation, with atomic ablator-gas mix playing a secondary role. In addition, spherical shells with pre-imposed 2D modulations were used to measure instability growth in the acceleration phase of the implosions. The capsules were imploded using ignition-relevant laser pulses, and ablation-front modulation growth was measured using x-ray radiography for a shell convergence ratio of ∼2. The measured growth was in good agreement with that predicted, thus validating simulations for the fastest growing modulations with mode numbers up to 90 in the acceleration phase. Future experiments will be focused on measurements at higher convergence, higher-mode number modulations, and growth occurring during the deceleration phase.

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Section: Introductionmentioning

confidence: 85%

Hydrodynamic instability growth and mix experiments at the National Ignition Facility

et al. 2014

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“…While N120205 (Au) performed comparatively well achieving T ion of 3.4 keV, on N120213 (DU) T ion dropped to 1.9 keV and yield plummeted by a factor of 6× due to CH ablator material catastrophically mixing into the hot spot [8]. Conversely, the highest DSR and thus fuel ρR reported so far was achieved with a DU hohlraum on N120321 [6]. It had the same Au-equivalent hohlraum drive at P Au-eq laser ¼ 370 TW as N120417 (Au), resulting in the same neutron yield on these companion experiments.…”

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confidence: 93%

“…Experiments during the National Ignition Campaign (NIC) [4] demonstrated high implosion velocities (∼360 km=s) [5], and high areal mass densities of 1.3 AE 0.1 g=cm 2 [6], which were predicted to be sufficient to reach ignition [7]. However, some of them showed evidence for significant amounts of CH ablator material mixing into the hot spot [8,9], degrading the implosion performance.…”

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confidence: 99%

“…Higher-Z (than Au) hohlraums are predicted to help increase the capsule drive at a given P laser and provide a more symmetric hohlraum drive [4]. However, DT experiments using uranium hohlraums during the National Ignition Campaign gave mixed results-they showed one of the best [6] and some of the worst performance, which led us to question the benefits of uranium as a hohlraum material. Herein we will show the benefits of depleted uranium (DU) hohlraums for drive and hot-spot symmetry control compared to standard Au hohlraums in fully integrated DT implosion experiments.…”

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Demonstration of High Performance in Layered Deuterium-Tritium Capsule Implosions in Uranium Hohlraums at the National Ignition Facility

Döppner¹,

Callahan²,

Hurricane³

et al. 2015

Phys. Rev. Lett.

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We report on the first layered deuterium-tritium (DT) capsule implosions indirectly driven by a "highfoot" laser pulse that were fielded in depleted uranium hohlraums at the National Ignition Facility. Recently, high-foot implosions have demonstrated improved resistance to ablation-front Rayleigh-Taylor instability induced mixing of ablator material into the DT hot spot [Hurricane et al., Nature (London) 506, 343 (2014)]. Uranium hohlraums provide a higher albedo and thus an increased drive equivalent to an additional 25 TW laser power at the peak of the drive compared to standard gold hohlraums leading to higher implosion velocity. Additionally, we observe an improved hot-spot shape closer to round which indicates enhanced drive from the waist. In contrast to findings in the National Ignition Campaign, now all of our highest performing experiments have been done in uranium hohlraums and achieved total yields approaching 10 16 neutrons where more than 50% of the yield was due to additional heating of alpha particles stopping in the DT fuel. In indirect-drive inertial confinement fusion (ICF) [1,2], laser energy, converted to thermal x rays inside a high-Z cavity (hohlraum), ablatively drives the implosion of a spherical capsule containing a deuterium-tritium (DT) fuel layer. A high-velocity, low-entropy, highly symmetric implosion is required to form a hot spot of sufficiently high density and temperature from a combination of PdV work and alpha particle deposition. Above the ignition threshold, a self-sustained nuclear burn wave is launched igniting the surrounding compressed fuel layer. Ignition and burn is predicted for stagnation pressures above 300 Gbar [3].Experiments during the National Ignition Campaign (NIC) [4] demonstrated high implosion velocities (∼360 km=s) [5], and high areal mass densities of 1.3 AE 0.1 g=cm 2 [6], which were predicted to be sufficient to reach ignition [7]. However, some of them showed evidence for significant amounts of CH ablator material mixing into the hot spot [8,9], degrading the implosion performance. To increase the resistance to hydrodynamic instabilities [10], the "high-foot" drive design was developed [11,12], which has demonstrated an order-of-magnitude improvement in neutron yields with first evidence for additional heating from alpha particle stopping [13]. The high-foot drive raises the hohlraum temperature to 90 eV during the foot, launching a stronger first shock and sets the implosion on a higher adiabat. Among the benefits are a larger ablator density scale length (reducing susceptibility to ablation front RayleighTaylor growth [14]), and a shorter, simplified laser drive (three shocks rather than four). These benefits come at the price of lower fuel areal density, which requires higher implosion velocity compared to the low-entropy design [7] to achieve ignition.The first high-foot DT implosions [12,13,15] were done in gold (Au) hohlraums. These experiments incrementally increased laser peak power P laser and thus total laser energy from 351 TW=1.3 MJ on N13...

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“…Mixture properties play a significant role in inertial confinement fusion (ICF). For example, mixing of the plastic ablator into the fuel has been used to partially explain lower than expected yields in experiments [1][2][3][4]. Understanding this behavior is crucial, so much so that experiments are designed to monitor and control mixing of the ablator into the fuel.…”

Section: Introductionmentioning

confidence: 99%

Transport properties of an asymmetric mixture in the dense plasma regime

et al. 2016

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We study how concentration changes ionic transport properties along isobars-isotherms for a mixture of hydrogen and silver, representative of turbulent layers relevant to inertial confinement fusion (ICF) and astrophysics. Hydrogen will typically be fully ionized while silver will be only partially ionized but can have a large effective charge. This will lead to very different physical conditions for the H and Ag. Large first principles orbital free molecular dynamics (OFMD) simulations are performed and the resulting transport properties are analyzed. Comparisons are made with transport theory in the kinetic regime and in the coupled regime. The addition of a small amount of heavy element in a light material has a dramatic effect on viscosity and diffusion of the mixture. This effect is explained through kinetic theory as a manifestation of a crossover between classical diffusion and Lorentz diffusion.

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Performance of High-Convergence, Layered DT Implosions with Extended-Duration Pulses at the National Ignition Facility

Cited by 49 publications

References 32 publications

Hydrodynamic instability growth and mix experiments at the National Ignition Facility

Hydrodynamic instability growth and mix experiments at the National Ignition Facility

Demonstration of High Performance in Layered Deuterium-Tritium Capsule Implosions in Uranium Hohlraums at the National Ignition Facility

Transport properties of an asymmetric mixture in the dense plasma regime

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