Direct drive: Simulations and results from the National Ignition Facility

Radha, P. B.; Hohenberger, M.; Edgell, D. H.; Marozas, J.A.; Marshall, F. J.; Michel, D. T.; Rosenberg, Michael J.; Seka, W.; Shvydky, A.; Boehly, T. R.; Collins, T. J. B.; Campbell, E. M.; Craxton, R. S.; Delettrez, J. A.; Dixit, S. N.; Frenje, J. A.; Froula, D. H.; Goncharov, V. N.; Hu, S. X.; Knauer, J. P.; McCrory, R. L.; McKenty, P. W.; Meyerhofer, D. D.; Moody, J. D.; Myatt, J. F.; Petrasso, R. D.; Regan, S. P.; Sangster, T. C.; Sio, H.; Skupsky, S.; Zylstra, A. B.

doi:10.1063/1.4946023

Cited by 42 publications

(13 citation statements)

References 45 publications

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“…In the cross-beam energy transfer (CBET) process [16], nonabsorbed light that is reflected or scattered from its critical surface or refracted from the underdense plasma acts as an electromagnetic seed for the stimulated Brillouin scatter of incoming (incident) light [17]. CBET has been shown to reduce the target absorption and resulting P abl of direct-drive ICF targets by as much as 40% on OMEGA [16] and 60% on NIF-scale targets [18]; hydrodynamic instabilities and lowmode drive asymmetries can reduce P hs and neutron rate, and the suprathermal electron generation by the twoplasmon-decay instability and stimulated Raman scattering [19] can preheat the DT fuel and raise α.…”

Section: =3mentioning

confidence: 99%

Demonstration of Fuel Hot-Spot Pressure in Excess of 50 Gbar for Direct-Drive, Layered Deuterium-Tritium Implosions on OMEGA

Regan¹,

Goncharov²,

Igumenshchev³

et al. 2016

Phys. Rev. Lett.

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A record fuel hot-spot pressure P hs ¼ 56 AE 7 Gbar was inferred from x-ray and nuclear diagnostics for direct-drive inertial confinement fusion cryogenic, layered deuterium-tritium implosions on the 60-beam, 30-kJ, 351-nm OMEGA Laser System. When hydrodynamically scaled to the energy of the National Ignition Facility, these implosions achieved a Lawson parameter ∼60% of the value required for ignition [A. Bose et al., Phys. Rev. E 93, LM15119ER (2016)], similar to indirect-drive implosions [R. Betti et al., Phys. Rev. Lett. 114, 255003 (2015)], and nearly half of the direct-drive ignition-threshold pressure. Relative to symmetric, one-dimensional simulations, the inferred hot-spot pressure is approximately 40% lower. Three-dimensional simulations suggest that low-mode distortion of the hot spot seeded by laserdrive nonuniformity and target-positioning error reduces target performance. DOI: 10.1103/PhysRevLett.117.025001 The spherical concentric layers of a direct-drive inertial confinement fusion (ICF) target nominally consist of a central region of a near-equimolar deuterium and tritium (DT) vapor surrounded by a cryogenic DT-fuel layer and a thin, nominally plastic (CH) ablator. The outer surface of the ablator is uniformly irradiated with multiple laser beams having a peak overlapped intensity of <10 15 watts=cm 2 . The resulting laser-ablation process causes the target to accelerate and implode. As the DT-fuel layer decelerates, the initial DT vapor and the fuel mass thermally ablated from the inner surface of the ice layer are compressed and form a central hot spot, in which fusion reactions occur. ICF relies on the 3.5-MeV DT-fusion alpha particles depositing their energy in the hot spot, causing the hotspot temperature to rise sharply and a thermonuclear burn wave to propagate out through the surrounding nearly degenerate, cold, dense DT fuel, producing significantly more energy than was used to heat and compress the fuel. Ignition is predicted to occur when the product of the temperature and areal density of the hot spot reach a minimum of 5 keV × 0.3 g=cm 2 [1-3]. Currently, the 192-beam, 351-nm, 1.8-MJ National Ignition Facility (NIF) [4] is configured for indirectdrive-ignition experiments using laser-driven hohlraums to accelerate targets via x-ray ablation. Approximately 26 kJ of thermonuclear fusion energy has been recorded on the NIF using indirect-drive ICF targets [5], where alpha heating has boosted the fusion yield by a factor of ∼2.5 from that caused by the implosion system alone [6,7]. The indirect-drive NIF implosions have achieved over 60% of the Lawson parameter Pτ required for ignition, where P is the pressure and τ is the confinement time [6]. Here P and τ are estimated without accounting for alpha heating to assess the pure hydrodynamic performance. The goal of achieving laboratory fusion and progress made with direct-drive ICF over the last decade motivate direct-drive implosions on NIF [8,9]. Hot-spot formation for spherically symmetric, direct-drive, DT-layered implosions is st...

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Section: =3mentioning

confidence: 99%

Demonstration of Fuel Hot-Spot Pressure in Excess of 50 Gbar for Direct-Drive, Layered Deuterium-Tritium Implosions on OMEGA

Regan¹,

Goncharov²,

Igumenshchev³

et al. 2016

Phys. Rev. Lett.

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“…We use a laser ray trace method for depositing the energy in the capsule, which takes into account the 3D pointing geometry, but does not include the effects of cross-beam energy transfer or nonlocal electron thermal transport. Both of these effects are known to be important for modeling laser-matter interactions in direct drive implosions, [24,25,26] but we have nonetheless found that the salient features of our shots are modeled well using a more approximate treatment. Our models employ multigroup diffusion for the propagation of radiation, and we apply a flux limiter to the electron ther- mal conduction in the ablator during the laser pulse.…”

Section: Model Description and Resultsmentioning

confidence: 83%

Comparison of ablators for the polar direct drive exploding pusher platform

Whitley,

Kemp,

Yeamans

et al. 2020

Preprint

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We examine the performance of pure boron, boron carbide, high density carbon, and boron nitride ablators in the polar direct drive exploding pusher (PDXP) platform. The platform uses the polar direct drive configuration at the National Ignition Facility to drive high ion temperatures in a room temperature capsule and has potential applications for plasma physics studies and as a neutron source. The higher tensile strength of these materials compared to plastic enables a thinner ablator to support higher gas pressures, which could help optimize its performance for plasma physics experiments, while ablators containing boron enable the possiblity of collecting addtional data to constrain models of the platform. Applying recently developed and experimentally validated equa-$ Manuscript prepared for the proceedings of IFSA2019.

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“…26. This has been shown to work well in PDD experiments with thicker CH shells, 43,44 and has also been used to design pointings for earlier NIF PDD exploding pusher implosions, including N120328. 37 Time-resolved x-ray images obtained on reference shot N120328 showed a fairly substantial non-uniformity with the implosion being oblate (diameter ~940 m by 800 m) in-flight at t=1.14 ns, even though SAGE simulations indicated that the implosion should be symmetric.…”

Section: Fig 7 Dmentioning

confidence: 97%

Development of an inertial confinement fusion platform to study charged-particle-producing nuclear reactions relevant to nuclear astrophysics

et al. 2017

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This paper describes the development of a platform to study astrophysically relevant nuclear reactions using inertial-confinement fusion implosions on the OMEGA and National Ignition Facility laser facilities, with a particular focus on optimizing the implosions to study charged-particle-producing reactions. Primary requirements on the platform are high yield, for high statistics in the fusion product measurements, combined with low areal density, to allow the charged fusion products to escape. This is optimally achieved with direct-drive exploding pusher implosions using thin-glass-shell capsules. Mitigation strategies to eliminate a possible target sheath potential which would accelerate the emitted ions are discussed. The potential impact of kinetic effects on the implosions is also considered. The platform is initially employed to study the complementary T(t,2n)α, T(3He,np)α and 3He(3He,2p)α reactions. Proof-of-principle results from the first experiments demonstrating the ability to accurately measure the energy and yields of charged particles are presented. Lessons learned from these experiments will be used in studies of other reactions. The goals are to explore thermonuclear reaction rates and fundamental nuclear physics in stellar-like plasma environments, and to push this new frontier of nuclear astrophysics into unique regimes not reachable through existing platforms, with thermal ion velocity distributions, plasma screening, and low reactant energies.

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Direct drive: Simulations and results from the National Ignition Facility

Cited by 42 publications

References 45 publications

Demonstration of Fuel Hot-Spot Pressure in Excess of 50 Gbar for Direct-Drive, Layered Deuterium-Tritium Implosions on OMEGA

Demonstration of Fuel Hot-Spot Pressure in Excess of 50 Gbar for Direct-Drive, Layered Deuterium-Tritium Implosions on OMEGA

Comparison of ablators for the polar direct drive exploding pusher platform

Development of an inertial confinement fusion platform to study charged-particle-producing nuclear reactions relevant to nuclear astrophysics

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