Technical development of sound velocity and density measurements of liquid iron alloys up to Martian core conditions

2016 Fiscal Year Final Research Report

• Project/Area Number: 26800231
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Solid earth and planetary physics
• Research Institution: The University of Tokyo
• Principal Investigator: Nishida Keisuke 東京大学, 大学院理学系研究科(理学部), 助教 (40530887)
• Project Period (FY): 2014-04-01 – 2017-03-31
• Keywords: 火星核 / 月核 / 液体 / 音速 / 高温高圧 / 鉄合金 / 地球核 / 密度

Outline of Final Research Achievements

We set up an in-situ sound velocity measurements system using ultrasonic pulse echo method combined with synchrotron X-ray technique and Kawai-type multi-anvil apparatus at AR-NE7A beamline of KEK PF. We conducted additional experiments and reanalyses of previous data to solve the discrepancy among the sound velocities in liquid Fe-S reported by different research groups. We proposed new density and velocity model of the Moon's core.
We developed techniques to measure sound velocity in liquid Fe alloys up to 20 GPa. The size and materials of parts of high-pressure cell were optimized to maintain parallel between the front and back surfaces of the sample at high pressure and high temperature. We developed an ultrasonic transducer with high-sensitivity and broad bandwidth. We successfully measured sound velocity in liquid Fe80S20 up to 20 GPa with an error of 1% at the best, and with an error of 2.5% even at the highest pressure.

Free Research Field

高圧地球科学