Status of our understanding and modeling of x-ray coupling efficiency in laser heated hohlraums

Dattolo, E.; Suter, L. J.; Monteil, M. C.; Jadaud, J. P.; Dague, N.; Glenzer, S. H.; Turner, R. E.; Juraszek, D.; Lasinski, B. F.; Decker, C. D.; Landen, O. L.; MacGowan, B. J.

doi:10.1063/1.1324659

Cited by 29 publications

(20 citation statements)

References 13 publications

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“…However, when beams are obliquely incident (i.e., hit the side walls), models only agree with measurements for cans with a diameter of 1000 μm or larger [5]. Here we demonstate agreement for laser beams obliquely propagating into cans with a 400 μm diameter (c.f.…”

Section: Creation Of Hot Radiation Environments In Laser-driven Targetssupporting

confidence: 55%

Creation of Hot Radiation Environments in Laser-Driven Targets

et al. 2006

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Section: Creation Of Hot Radiation Environments In Laser-driven Targetssupporting

confidence: 55%

Creation of Hot Radiation Environments in Laser-Driven Targets

et al. 2006

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“…[10][11][12][13] We find that simulations using less conservative atomic physics and electron heat transport models agree with the measurements and indicate a hohlraum x-ray conversion efficiency of approximately 90%. We find that the total reflected energy due to laser backscatter instabilities is less than 2% of the total incident energy.…”

supporting

confidence: 67%

Observation of High Soft X-Ray Drive in Large-Scale Hohlraums at the National Ignition Facility

Kline¹,

Glenzer²,

Olson³

et al. 2011

Phys. Rev. Lett.

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“…With η CE being the x-ray conversion efficiency from laser power to soft x-rays [57,58]; α W and α CAP are the x-ray albedo of the hohlraum wall and the capsule, respectively. The albedo is defined as the ratio of re-emitted to incident x-rays.…”

Section: Laser and Hohlraum Drivementioning

confidence: 99%

Cryogenic thermonuclear fuel implosions on the National Ignition Facility

et al. 2012

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The first inertial confinement fusion implosion experiments with equimolar deuterium-tritium thermonuclear fuel have been performed on the National Ignition Facility. These experiments use 0.17 mg of fuel with the potential for ignition and significant fusion yield conditions. The thermonuclear fuel has been fielded as a cryogenic layer on the inside of a spherical plastic capsule that is mounted in the center of a cylindrical gold hohlraum. Heating the hohlraum with 192 laser beams for a total laser energy of 1.6 mega joules produces a soft x-ray field with 300 eV temperature. The ablation pressure produced by the radiation field compresses the initially 2.2-mm diameter capsule by a factor of 30 to a spherical dense fuel shell that surrounds a central hot-spot plasma of 50 µm diameter. While an extensive set of x-ray and neutron diagnostics has been applied to characterize hot spot formation from the x-ray emission and 14.1 MeV deuterium-tritium primary fusion neutrons, thermonuclear fuel assembly is studied by measuring the down-scattered neutrons with energies in the range of 10 to 12 MeV. X-ray and neutron imaging of the compressed core and fuel indicate a fuel thickness of (14 ± 3) µm, which combined with magnetic recoil spectrometer measurements of the fuel areal density of (1 ± 0.09) g cm −2 result in fuel densities approaching 600 g cm −3 . The fuel surrounds a hot-spot plasma with average ion temperatures of (3.5 ± 0.1) keV that is measured with neutron time of flight spectra. Absolute neutron yields of (7.5 ± 0.1) × 10 14 have been recorded from the magnetic recoil spectrometer and nuclear activation diagnostics while gamma ray measurements provide the duration of nuclear activity of (170 ± 30) ps. These indirect-drive implosions result in the highest areal densities and neutron yields achieved on laser facilities to date. This achievement is the result of the first hohlraum and capsule tuning experiments where the stagnation pressures have been systematically increased by more than a factor of 10 by fielding low-entropy implosions through the control of radiation symmetry, small hot electron production, and proper shock timing. The stagnation pressure is above 100 Gbar resulting in high Lawson confinement parameters of P τ 10 atm s. Comparisons with radiation-hydrodynamic simulations indicate that the pressure is within a factor of three required for reaching ignition and high yield. This will be the focus of future higher-velocity implosions that will employ additional optimizations of hohlraum, capsule and laser pulse shape conditions.

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Status of our understanding and modeling of x-ray coupling efficiency in laser heated hohlraums

Cited by 29 publications

References 13 publications

Creation of Hot Radiation Environments in Laser-Driven Targets

Creation of Hot Radiation Environments in Laser-Driven Targets

Observation of High Soft X-Ray Drive in Large-Scale Hohlraums at the National Ignition Facility

Cryogenic thermonuclear fuel implosions on the National Ignition Facility

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