Matter and Radiation at Extremes, Volume. 6, Issue 5, 054403(2021)

In situ observation of the Rayleigh–Taylor instability of liquid Fe and Fe–Si alloys under extreme conditions: Implications for planetary core formation

Hidenori Terasaki1...2,a), Tatsuhiro Sakaiya1, Keisuke Shigemori3, Kosaku Akimoto1, Hiroki Kato3, Yoichiro Hironaka3 and Tadashi Kondo1 |Show fewer author(s)
Author Affiliations
  • 1Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
  • 2Department of Earth Sciences, Graduate School of Science and Technology, Okayama University, Okayama 700-8530, Japan
  • 3Institute of Laser Engineering, Osaka University, Suita, Osaka 565-0871, Japan
  • show less
    Figures & Tables(6)
    Initial perturbation on the Fe–10 wt. % Si (No. 39 836) sample. (a) Laser scanning microscope images of initial perturbation on the sample surface. (b) Horizontal line profiles of the surface perturbation at the vertical center of the sample. The initial wavelength and amplitude of the perturbation in the fundamental mode are 80 ± 0.7 and 2.3 ± 0.1 µm, respectively. (c) Amplitudes of each mode of the perturbation obtained by Fourier analysis. Here, 80 and 27 µm indicate the perturbation wavelengths of the fundamental and third modes, respectively.
    Schematic of experimental setup for face-on radiography. The drive laser and x-rays for radiography measurements come from the same direction onto the sample. The characteristic lengths are as follows: the backlighter–sample distance is 3 mm, the sample–slit distance is 50 mm, and the slit–XSC distance is 1450 mm. The direction of effective gravity is shown by the black arrow. This direction and that of the perturbation interface are consistent with the setting of the core formation scenario (accumulated Fe alloy on the mantle).
    X-ray radiography images of (a) Fe (No. 38 472) and (b) Fe–10 wt. % Si (No. 39 836) from face-on radiography. The bright areas correspond to higher x-ray transmitted intensity, indicating thinner parts of the sample perturbation. (c) Spatial line-scan profiles of (a) at early time (t = 1.1 ns) and later time (t = 2.1 ns). (d) Spatial line-scan profiles of (b) at early time (t = 1.2 ns) and later time (t = 2.3 ns). The dotted curves indicate the background profiles of x-ray intensity, i.e., the profiles of the backlight x-rays. The fundamental modes analyzed are shown by arrows, and the corresponding wavelengths are 62 µm for Fe and 80 µm for Fe–10 wt. % Si.
    Temporal variation of the growth factor G: (a) Fe–10 wt. % Si and Fe–20 wt. % Si; (b) Fe; (c) Fe–20 wt. % Si and Fe–20 wt. % Si + forsterite (Fo); (d) Fe and Fe + Fo. The RT instability regime corresponds to the period shown by the filled symbols. Dotted lines indicate fits of the data in the RT instability regime using Eq. (5) to obtain γ. Shaded bands indicate the standard deviation of the data shown by the filled symbols.
    Growth rate γ as a function of Si content. The obtained γ of Fe (Nos. 38 472 and 39 834), Fe–10 wt. % Si (No. 39 836), and Fe–20 wt. % Si (No. 39 839) are plotted. The shaded area indicates the effect of Si on γ, including the error.
    • Table 1. Sample compositions and conditions of initial perturbation.a

      View table
      View in Article

      Table 1. Sample compositions and conditions of initial perturbation.a

      Shot No.Sample compositionSurface coatingInitial density ρ0 (g/cm3)Initial thickness d0 (μm)Initial amplitude of perturbation l0 (μm)Initial wavelength of perturbation λ0 (μm)
      38 472Fe7.811.6 (0.6)1.0 (0.1)62 (0.4)
      39 834Fe7.86.2 (0.4)0.9 (0.1)80 (0.7)
      38 470FeForsterite7.811.6 (0.6)0.9 (0.1)62 (0.4)
      39 836Fe–10 wt. % Si7.316.0 (4.0)2.3 (0.1)80 (0.7)
      39 839bFe–20 wt. % Si6.87.5 (2.5)2.8 (0.1)80 (0.7)
      39 853Fe–20 wt. % SiForsterite6.87.5 (2.5)2.9 (0.1)80 (0.7)
    Tools

    Get Citation

    Copy Citation Text

    Hidenori Terasaki, Tatsuhiro Sakaiya, Keisuke Shigemori, Kosaku Akimoto, Hiroki Kato, Yoichiro Hironaka, Tadashi Kondo. In situ observation of the Rayleigh–Taylor instability of liquid Fe and Fe–Si alloys under extreme conditions: Implications for planetary core formation[J]. Matter and Radiation at Extremes, 2021, 6(5): 054403

    Download Citation

    EndNote(RIS)BibTexPlain Text
    Save article for my favorites
    Paper Information

    Category: Fundamental Physics At Extreme Light

    Received: Sep. 13, 2020

    Accepted: Aug. 2, 2021

    Published Online: Oct. 19, 2021

    The Author Email: Terasaki Hidenori (tera@okayama-u.ac.jp)

    DOI:10.1063/5.0029448

    Topics