Research ArticlePHYSICS

Energy penetration into arrays of aligned nanowires irradiated with relativistic intensities: Scaling to terabar pressures

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Science Advances  11 Jan 2017:
Vol. 3, no. 1, e1601558
DOI: 10.1126/sciadv.1601558
  • Fig. 1 Schematic diagram, composition map, and x-ray spectrum of a two-composition Ni-Co nanowire array.

    (A) Schematic diagram of segmented two-composition Ni-Co nanowire array. The top Ni segment ranges in length from 1 to 6 μm. The nanowires are 55 nm in diameter and form an array that is 13% of solid density. (B) Scanning electron microscopy image with energy-dispersive spectroscopic elemental composition measurement indicating the concentration of Ni (blue) and Co (red). (C) Example spectra showing the He-like line dominance over the Kα lines for the two elements as recorded using a von Hamos crystal spectrometer. A.U., arbitrary units.

  • Fig. 2 Measured spectra of Ni-Co–segmented nanowire arrays with different lengths of Ni wires (listed in the top right corner of each plot) on top of cobalt wires, irradiated by 55-fs pulses at an intensity of ~4 × 1019 W cm−2.

    The vertically aligned wires are 55 nm in diameter and form an array that has an average atomic density that is 13% of solid density. Lines of He-like and Li-like Ni and Co are visible along with their respective Kα lines.

  • Fig. 3 Measured intensities of the He-like Co and Ni lines as a function of the length of the top Ni nanowire segment.

    The target and laser parameters are the same as those in Fig. 2.

  • Fig. 4 Simulated spectra corresponding to arrays with different wire lengths used in the experiment are shown in the top three plots.

    The target and laser parameters are the same as those in Fig. 2. Measured and simulated (Co He-α)/(Ni He-α) line ratios as a function of Ni nanowire segment length are shown on the bottom.

  • Fig. 5 PIC simulation of the density of He-like ions in an array composed of segments of vertically aligned Ni and Co nanowires (blue, He-like Ni; red, He-like Co).

    The target and laser parameters are the same as those in Fig. 2. The top Ni wires are 3.0 μm in length. The laser pulse impinges from the top at normal incidence to the array.

  • Fig. 6 ED distribution computed by PIC simulation.

    The target and laser parameters are the same as those in Fig. 5. Each frame corresponds to a different time with respect to the peak of the laser pulse as indicated by the time stamp in the top left corner of each frame. The laser pulse impinges into the array from the top at normal incidence.

  • Fig. 7 PIC-simulated energy density distribution in an array of vertically aligned 400-nm-diameter Au nanowires irradiated with an intensity of 1 × 1022 W cm−2 (a0 = 34) using a 400-nm wavelength pulse of 30-fs duration.

    The average atomic density is 12% of solid density. Each frame corresponds to a different time with respect to the peak of the laser pulse. The laser pulse impinges into the array from the top at normal incidence.

  • Fig. 8 Ion charge distribution as a function of depth for an array of 400-nm-diameter Au nanowires with 12% of solid density, irradiated at an intensity of 1 × 1022 W cm−2 as in Fig. 7.

    This plot was obtained by randomly choosing a fraction of the ions and placing a star at each charge and position. Groups of ionization stages are assigned different colors (for example, Z = 66 to 70 is blue) to accentuate the ion distribution and identify rare ions, such as the F-like ions in the bottom.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/1/e1601558/DC1

    Supplementary section

    fig. S1. Spectrum of an array of 55-nm-diameter Ni nanowires with an average atomic density corresponding to 30% of solid density irradiated at 4 × 1019 W cm−2 with an ultrahigh contrast λ = 400-nm laser pulse of 55-fs duration.

    fig. S2. Computed electron density distribution in 400-nm-diameter gold nanowire irradiated at an intensity of 1 × 1022 W cm−2 with a 30-fs laser pulse, corresponding to the conditions in Fig. 7.

    fig. S3. Electron energy distribution under the same irradiation conditions as in fig. S2 at different times with respect to the peak of the laser pulse averaged in space.

    fig. S4. Computed scaling of the energy density deposited into Au nanowire arrays as a function of the irradiation intensity for two different times during the plasma evolution.

    fig. S5. Ratio of kinetic energy density to pressure (α) as a function of the ratio of kinetic energy density to rest mass energy density (β).

    table S1. Pressures calculated from the kinetic energy density computed by the PIC simulations using the approximation by Ryu et al. (26).

  • Supplementary Materials

    This PDF file includes:

    • Supplementary section
    • fig. S1. Spectrum of an array of 55-nm-diameter Ni nanowires with an average atomic density corresponding to 30% of solid density irradiated at 4 × 1019 W cm−2 with an ultrahigh contrast λ = 400-nm laser pulse of 55-fs duration.
    • fig. S2. Computed electron density distribution in 400-nm-diameter gold nanowire irradiated at an intensity of 1 × 1022 W cm−2 with a 30-fs laser pulse, corresponding to the conditions in Fig. 7.
    • fig. S3. Electron energy distribution under the same irradiation conditions as in fig. S2 at different times with respect to the peak of the laser pulse averaged in space.
    • fig. S4. Computed scaling of the energy density deposited into Au nanowire arrays as a function of the irradiation intensity for two different times during the plasma evolution.
    • fig. S5. Ratio of kinetic energy density to pressure (α) as a function of the ratio of kinetic energy density to rest mass energy density (β).
    • table S1. Pressures calculated from the kinetic energy density computed by the PIC simulations using the approximation by Ryu et al. (26).

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