Dynamics of high-<i>Z</i>plasmas produced by a short-wavelength laser

Goldstone, P. D.; Goldman, S. R.; Mead, W. C.; Cobble, J. A.; Stradling, G. L.; Day, R. H.; Hauer, A.; Richardson, Martin; Marjoribanks, R. S.; Jaanimagi, P. A.; Keck, R. L.; Marshall, F. J.; Seka, W.; Barnouin, O.; Yaakobi, B.; Letzring, S.

doi:10.1103/physrevlett.59.56

Cited by 75 publications

(11 citation statements)

References 16 publications

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“…The experimentally measured spectrum taken from the above paper is shown in figure 6 by dashed-dotted line. Similar structure in the spectra was also measured in OMEGA experiments on gold-coated spheres [39]. It shows a strong peak at about 200 eV.…”

Section: Laser-driven Gold Foilmentioning

confidence: 58%

Effects of non-local thermodynamic equilibrium conditions on numerical simulations of inertial confinement fusion plasmas

Gupta

Godwal

2002

Pramana - J Phys

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Effects of non-local thermodynamic equilibrium (non-LTE) condition on emission and hydrodynamics of typical inertial confinement fusion (ICF) plasmas are studied. The average degree of ionization at high temperatures is seen to be much lower compared to the values obtained from Thomas-Fermi scaling or Saha equation for high-Z element like gold. LTE and non-LTE predictions for emitted radiation from laser-driven gold foil are compared with the experimental results and it is seen that non-LTE simulations show a marked improvement over LTE results. The effects of one group and multigroup, LTE and non-LTE approximations of radiation transport on hydrodynamic parameters are studied for laser-driven aluminium and gold foils. It is further seen that non-LTE and multigroup effects play an important role in predicting conversion efficiency of laser light to X-rays.

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Section: Laser-driven Gold Foilmentioning

confidence: 58%

Effects of non-local thermodynamic equilibrium conditions on numerical simulations of inertial confinement fusion plasmas

Gupta

Godwal

2002

Pramana - J Phys

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“…2). Besides laser uniformity onto target and time resolution, another significant difference to previous studies [11] performed in Au is the assessment of laser coupling onto the targets by measuring the backscattered light with FABS and NBI. Using the laser coupled into the target rather than the incident laser power yielded higher conversion efficiency than in [11].…”

Section: Discussionmentioning

confidence: 87%

“…Besides laser uniformity onto target and time resolution, another significant difference to previous studies [11] performed in Au is the assessment of laser coupling onto the targets by measuring the backscattered light with FABS and NBI. Using the laser coupled into the target rather than the incident laser power yielded higher conversion efficiency than in [11]. Furthermore, the conversion efficiency reaches a fairly constant plateau after 0.5 ns from the beginning of the laser pulse, when the radiative and hydrodynamic losses in the high-Z plasmas are balanced by the laser plasma heating by inverse bremmsstrahlung [19].…”

Section: Discussionmentioning

confidence: 87%

“…In such experiments it is therefore quite difficult to assess the validity of the x-ray emission models used in our ICF designs. For these reasons, in the present work, the soft x-ray conversion efficiency was measured in a convergent direct drive-like set-up [11], on spheres made of Au, cocktail and U uniformly heated by laser beams at the Omega Laser Facility [12]. The absolute soft x-ray flux in the 100 eV to 5 keV spectral range was measured temporally resolved with the Dante broadband spectrometer [14].…”

Section: Introductionmentioning

confidence: 99%

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X-ray conversion efficiency of high-Z hohlraum wall materials for indirect drive ignition

et al. 2008

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We measure the conversion efficiency of 351 nm laser light to soft x-rays (0.1-5 keV) for Au, U and high Z mixtures "cocktails" used for hohlraum wall materials in indirect drive ICF. We use spherical targets in a direct drive geometry, flattop laser pulses and laser smoothing with phase plates to achieve constant and uniform laser intensities of 10 14 and 10 15 W/cm 2 over the target surface that are relevant for the future ignition experiments on NIF. The absolute time and spectrally-resolved radiation flux is measured with a multichannel soft x-ray power diagnostic. The conversion efficiency is then calculated by dividing the measured x-ray power by the incident laser power from which the measured laser backscattering losses is subtracted. After ~0.5 ns, the time resolved x-ray conversion efficiency reaches a slowly increasing plateau of 95% at 10 14 W/cm 2 laser intensity and of 80% at 10 15 W/cm 2 . The M-band flux (2-5 keV) is negligible at 10 14 W/cm 2 reaching ~1% of the total x-ray flux for all target materials. In contrast, the Mband flux is significant and depends on the target material at 10 15 W/cm 2 laser intensity, reaching values between 10% of the total flux for U and 27% for Au. Our LASNEX simulations show good agreement in conversion efficiency and radiated spectra with data when using XSN atomic physics model and a flux limiter of 0.15, but they underestimate the generated M-band flux. I IntroductionIn indirect drive inertial confinement fusion (ICF) experiments, intense laser or charged particle beams heat the interior of high-Z cylindrical cavities called hohlraums to efficiently generate soft x-rays. The role of the soft x-rays is to uniformly produce an ablation drive that compresses the DT filled capsule placed inside the hohlraum, driving it to ignition and burn [1]. Due to the relaxed requirements on laser-beam uniformity and reduced sensitivity to hydrodynamic instabilities the indirect drive scenario is the main approach for future ignition experiments at the National Ignition Facility (NIF) [2,3,4]. In such a hohlraum containing a capsule and heated by laser beams the power balance is given by [5,6]:η CE (P laser -P backscatter ) = P walls +P LEH + P capsule =σT R 4 [(1-α)A wall +A LEH +f capsule A capsule ] (1) where η CE is the laser conversion efficiency into soft x-rays (<2 keV), P laser is the incident laser power, P backscatter is the backscattered light by parametric laser-plasma instabilities, P capsule is the radiation absorbed by the capsule, P LEH is the radiation escaping through the hohlraum laser entrance holes (LEH) and P walls is the radiation loss in the hohlraum walls.Furthermore, σ is the Stefan-Boltzmann constant, T R is the hohlraum radiation temperature (≤300 eV), α is the x-ray albedo of the hohlraum wall [7], defined as the ratio between the re-emitted and incident soft x-ray flux at the hohlraum wall, A wall and A LEH are the areas of the hohlraum wall and LEH's, f capsule is the fraction of incident x-ray flux that is absorbed by the capsule and A ...

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“…This value is not much different from the value of g =0.5 which, in agreement with planar target experiments, was adopted in Refs. [12] and [13], and which leads to good agreement between the measured and calculated temperature.…”

Section: A Similarity Modelmentioning

confidence: 57%

Experimental investigation of radiation heat waves driven by laser-induced Planck radiation

et al. 1992

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The propagation of a radiation heat wave through a thin foil of solid gold was investigated experimentally. The wave is driven by the intense thermal radiation in 1 -3-mm-diam gold cavities heated by an intense laser pulse (duration 0.8 -0.9 ns, wavelength 0.35 pm) to temperatures ranging from 80 to 240 eV.Evidence of the propagating wave was obtained from the delayed onset of thermal emission from the outer side of the foil. A detailed comparison of the results with the self-similar solution for the ablative heat wave and with numerical simulations is presented.PACS number(s): 52.50. Jm, 44.40.+a, 47.70.Mc

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Dynamics of high-Zplasmas produced by a short-wavelength laser

Cited by 75 publications

References 16 publications

Effects of non-local thermodynamic equilibrium conditions on numerical simulations of inertial confinement fusion plasmas

Effects of non-local thermodynamic equilibrium conditions on numerical simulations of inertial confinement fusion plasmas

X-ray conversion efficiency of high-Z hohlraum wall materials for indirect drive ignition

Experimental investigation of radiation heat waves driven by laser-induced Planck radiation

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