負ミュオンビームによる月隕石の非破壊元素分析法

Non-destructive elemental analysis of lunar meteorites using negative muon beam

Chiu, I.-H.; 寺田 健太郎*; 大澤 崇人  ; Park, C.*; 竹下 聡史*; 三宅 康博*; 二宮 和彦*

Chiu, I.-H. ; Terada, Kentaro*; Osawa, Takahito; Park, C.*; Takashita, Soshi*; Miyake, Yasuhiro*; Ninomiya, Kazuhiko*

We report non-destructive elemental analysis in lunar meteorites using a negative muon beam at J-PARC. An experimental system combining with six Ge semiconductor detectors and a newly designed He analysis chamber for the Al quantitative analysis provides a high signal-to-noise ratio for the measurement of major elements from lunar rocks (Mg, Si, Fe, O, Ca, and Al). By applying the Monte Carlo simulation, we successfully determined the chemical compositions of two sides (at 0.33 mm depth from the sample surface) and center of the sample (at 0.96 mm depth) from the lunar meteorite DEW 12007. It suggests the three interior regions of DEW 12007 are likely mixtures of anorthosite and basalt clasts with of 52.3 and 47.7, 48.4 and 51.6, and 48.1 and 51.9 wt, respectively. This is the first quantitative analysis of a heterogeneous meteorite interior using a negative muon beam. Since the elemental analysis with a muon beam is non-destructive and highly sensitive to the light elements including C, N, and O, the protocols established in this study can be applicable for the initial characterization of returned samples from the south pole of the Moon.