4:10 PM - 4:25 PM
[SIT18-08] High temperature and pressure sound velocity measurements for iron-nickel alloys and metals
Keywords:Sound velocity, High temperature, High pressure, Inelastic x-ray scattering
The Earth's core is one of the most interesting topics in Earth science. The only directly observed information about the Earth's core is based on seismic observations. The seismic model, the Preliminary Reference Earth Model (PREM) [1], provides sound (compressional and shear wave) velocities and density as a function of the depth of the Earth. One of the most interesting topics that has been discussed for a long time is that iron, which is thought to be the main component of the Earth's core, cannot account for the sound velocity and density of the PREM inner core by pure iron alone, compared to the PREM and laboratory high-pressure experiments [2, 3].
To constrain the composition of the Earth's core, both high temperature and pressure density and sound velocity measurements of various materials from high-pressure experiments are needed. While density has been widely used in previous high-pressure experiments compared to PREM [2], sound velocity measurements have been limited due to experimental challenges [3]. Therefore, sound velocity measurements of various iron alloys and metals under high temperature and pressure conditions, and knowledge of the density and temperature dependence of sound velocity obtained from these experiments, are important for the discussion of the Earth's core.
In this study, we have performed the sound velocity measurements of iron-nickel alloys and rhenium metal at high temperatures and multi-megabar pressures using inelastic x-ray scattering (IXS) and x-ray diffraction (XRD) methods at BL43LXU of SPring-8. The IXS intensities were measured with a total of 16 analyzer crystals installed in BL43LXU using a Soller screen system [4] to reduce noise as much as possible. The IXS provides the relation between the change in momentum transfer and the change in energy, from which the sound velocity could be derived. The XRD patterns were measured under the same conditions using the flat panel detector, and the density of the sample could be calculated from the patterns. These results allow us to know the relations between sound velocity and density, and its temperature dependence.
We report these density and temperature dependencies, with comparisons to other materials from previous studies [5, 6], and implicate them in the discussion of the Earth's core.
References:
[1] Dziewonski and Anderson, Phys. Earth Planet. Inter. 25, 297-356 (1981).
[2] Dewaele et al., Phys. Rev. Lett. 97, 215504 (2006).
[3] Ikuta et al., Nat. Commun. 13, 7211 (2022).
[4] Baron et al., AIP Conf. Proc. 2054, 020002 (2019).
[5] Ikuta et al., JpGU Meeting 2023 (2023).
[6] Ikuta et al., JpGU Meeting 2024 (2024).
To constrain the composition of the Earth's core, both high temperature and pressure density and sound velocity measurements of various materials from high-pressure experiments are needed. While density has been widely used in previous high-pressure experiments compared to PREM [2], sound velocity measurements have been limited due to experimental challenges [3]. Therefore, sound velocity measurements of various iron alloys and metals under high temperature and pressure conditions, and knowledge of the density and temperature dependence of sound velocity obtained from these experiments, are important for the discussion of the Earth's core.
In this study, we have performed the sound velocity measurements of iron-nickel alloys and rhenium metal at high temperatures and multi-megabar pressures using inelastic x-ray scattering (IXS) and x-ray diffraction (XRD) methods at BL43LXU of SPring-8. The IXS intensities were measured with a total of 16 analyzer crystals installed in BL43LXU using a Soller screen system [4] to reduce noise as much as possible. The IXS provides the relation between the change in momentum transfer and the change in energy, from which the sound velocity could be derived. The XRD patterns were measured under the same conditions using the flat panel detector, and the density of the sample could be calculated from the patterns. These results allow us to know the relations between sound velocity and density, and its temperature dependence.
We report these density and temperature dependencies, with comparisons to other materials from previous studies [5, 6], and implicate them in the discussion of the Earth's core.
References:
[1] Dziewonski and Anderson, Phys. Earth Planet. Inter. 25, 297-356 (1981).
[2] Dewaele et al., Phys. Rev. Lett. 97, 215504 (2006).
[3] Ikuta et al., Nat. Commun. 13, 7211 (2022).
[4] Baron et al., AIP Conf. Proc. 2054, 020002 (2019).
[5] Ikuta et al., JpGU Meeting 2023 (2023).
[6] Ikuta et al., JpGU Meeting 2024 (2024).