JAXA Repository / AIREX 未来へ続く、宙(そら)への英知
Other TitleAn experimental study of permeable membrane for Ne isotope measurement aiming for future Mars mission
Author(jpn)奥野, 衛; 吉岡, 和夫; 三浦, 弥生; 長, 勇一郎; 齋藤, 義文; 杉田, 精司
Author(eng)Okuno, Mamoru; Yoshioka, Kazuo; Miura, Yayoi N.; Cho, Yuichiro; Saito, Yoshifumi; Sugita, Seiji
Author Affiliation(jpn)東京大学; 東京大学; 東京大学地震研究所; National Aeronautics and Space Administration (NASA); 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS); 東京大学
Author Affiliation(eng)The University of Tokyo; The University of Tokyo; Earthquake Research Institute, The University of Tokyo; National Aeronautics and Space Administration (NASA); Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS); The University of Tokyo
Issue Date2017-03-10
Japan Aerospace Exploration Agency (JAXA)
Publication title宇宙航空研究開発機構研究開発報告
JAXA Research and Development Report
Start page1
End page14
Publication date2017-03-10
AbstractWe are developing a Ne isotope measurement system with a permeable membrane for a future Mars mission. A typical lightweight mass spectrometer with moderate mass resolution (m/Δm approximately 10(exp 2)), such as a quadrupole mass spectrometer (QMS), cannot distinguish Ar-40(++) from Ne-20(+) signal because the difference in their mass/charge ratios is very small (m/Δm = 1777). Thus, Ar needs to be removed from sample gas before mass spectrometric measurements. One approach to separate Ne and Ar is to use a permeable membrane. In this study, we experimentally investigate the difference in permeability of Viton sheets between Ar and Ne. Our experimental results indicate that a 1-mm Viton sheet can increase the abundance ratio of Ne to Ar from the atmospheric value of approximately 10(exp -3) to approximately 1. We also measured the ratio of Ar-40(++) to Ar-40(+) using a QMS with a typical ionization voltage (70V). The results indicate that Ar-40(++) is generated about 10% of that of Ar-40(+) during the ionization process in the QMS. These results suggest that the Ne isotope measurement with the uncertainty better than 10% can be performed by correcting for the contribution of Ar-40(++). Since Martian atmospheric pressure is about two orders of magnitude lower and Ne-20/Ar-40 ratio is about one order of magnitude lower, the separation efficiency could decrease compared to that at the Earth atmosphere. However, it has a room for significant improvement by optimization for various parameters, such as materials, thickness, and duration of permeation. These results suggest that measurements of Ne isotopic ratio in Martian atmosphere can be achieved with this approach after optimization.
我々は将来の大気突入機等を用いた火星探査計画を念頭において、火星大気中に含まれるネオンの同位体測定を可能にすべく、簡便な分別膜を併用した質量分析装置の開発を進めている。本研究では四重極型質量分析計(QMS)を用いてNe-20とNe-22をそれぞれ測定する際に妨げとなるAr-40、(44)CO2の二価イオンを、分別膜を用いて物理的に排除する仕組みを検討し、軽量かつ高効率の観測装置の実現を目指している。具体的には、分別膜として厚さ1mm のバイトンシートを用いると、地球大気中では10(exp -3) 程度のNe-20/Ar-40存在比を、3桁程度向上させられるとの結果を得た。また、質量分析計のイオン化部において、70 Vという典型的なイオン化電圧では、Ar-40(+)に対して約10%のAr-40(++)が生成されることを確認した。この結果は、分別膜でNe-20/Ar-40 ~ 1に向上させれば、Ar-40(++)の補正をすることでNeの計測を誤差10%以下で実現できることを意味する。本研究は地球大気を用いた実験であるため、組成や分圧の異なる火星大気条件での膜に対する透過特性は今後検証する必要がある。しかし、分別膜の素材、厚み、透過時間等のパラメタを最適化することで分別効率をさらに向上できる余地も残っているため、本研究の結果は火星大気中でのNe同位体測定の実現可能性を強く示唆するものである。
Description形態: カラー図版あり
Physical characteristics: Original contains color illustrations
KeywordsMartian atmosphere; Ne measurement; mars mission; mass spectrometer; instrument development
Document TypeTechnical Report
JAXA Category研究開発報告
NASA Subject CategoryLunar and Planetary Science and Exploration
Report NoJAXA-RR-16-009

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