演題概要

1B-O1-1445（1P-20）

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同位体ナノスコープによる鉱物中のHe，Ne，Arの同時局所同位体分析法の開発

(¹北大院理・ ²ETH)
^o大槻悠太¹・ 馬上謙一¹・ 小長谷智哉¹・ Wieler, Rainer²・ 圦本尚義¹

The surfaces of airless celestial bodies are irradiated by solar wind. Because their abundances in natural minerals are extremely low, noble gases are useful as tracers of solar wind implantation. Solar wind noble gases are implanted into regolith grains with the implanted depths correlated to the solar wind speed. Therefore, depth distribution of implanted solar wind can be used to evaluate the speed distribution of the past solar wind. Recently, helium depth profiling of the NASA/Genesis target material was performed with an isotope nanoscope, and the depth distribution matched well with the simulated depth profile. However, other noble gases have not been measured in individual natural minerals. In this study, we developed the analytical conditions (i.e., time of flight, isotope and valence to be measured) to measure helium, neon, and argon isotopes in ilmenite and olivine, which are major minerals of lunar and asteroidal regolith. The detection limits of ⁴He, ^{20, 22}Ne, and ^{36, 40}Ar were (3, 0.3, 0.1, 0.4, 3) × 10¹⁷ cm⁻³ for ilmenite and (2, 0.9, 0.2, 0.3, 10) × 10¹⁷ cm⁻³ for olivine, respectively.