Determination of the energy spectrum of secondary neutron flux for lunar samples and its application for meteoritics

月球样品二次中子通量能谱测定及其在陨石学中的应用

• 批准号: 10640476
• 负责人: HIDAKA Hiroshi
• 金额: $ 2.5万
• 依托单位: Hiroshima University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1998
• 资助国家: 日本
• 起止时间: 1998 至 1999
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10640476/
• 关键词: lunar soil; aubrite; chondrite; cosmic-ray; neutron capture reaction; samarium; gadolinium; isotopic composition; 中性子捕獲; エネルギー共鳴; 隕石

The isotopic compositions of Sm and Gd in seven lunar samples from the Apollo 12 and 15 drill cores were determined to discuss the effects of neutron capture near the lunar surface. Neutron fluence values calculated from the isotopic shifts of A- 12 and A- 15 samples were (1.77 - 2.17) x10ィイD116ィエD1ncmィイD1-2ィエD1 and (3.02 - 4.68)x10ィイD116ィエD1 n cmィイD1-2ィエD1, respectively. Variations of εィイD2SmィエD2/εィイD2GdィエD2 with depth are interpreted as due to variations in the neutron energy spectrum. Our data suggest that the neutron is more thermalized at the lower layers than it is at the upper layers (Hidaka et al., in press).This approach was applied for meteoritics. Large isotopic deviations of ィイD1149ィエD1Sm-ィイD1150ィエD1Sm and ィイD1157ィエD1Gd-ィイD1158ィエD1Gd derived from neutron capture effects were observed in five enstatite achondrites (aubrites). The isotopic variations of these aubrites correspond to irradiation with neutron fluence of (1.17-3.99)x10ィイD116ィエD1 n cmィイD1-2ィエD1 which is within the … More range of estimated neutron fluence values of some lunar samples. These results indicate that aubrites may have been located near the surface of their parent body for several hundreds of Ma. Furthermore, the neutron energy spectrum obtained from the combination of Sm and Gd isotope systematics (εィイD2SmィエD2/εィイD2GdィエD2) suggests that the energy of thermalized neutrons in five aubrites was in the range from 200 〜 400 K, and was lower than those in A-12 and A-15 lunar samples (Hidaka et al., 1999). Isotopic compositions of Sm and Gd in eight chondrites show an evidence of neutron capture effects in the chondrites, correspond to thermal neutron fluences of (1.03 〜 5.17)x10ィイD115ィエD1 n cmィイD1-2ィエD1. The Sm and Gd isotopic results of four of eight chondrites were compared with information on epi-thermal and fast neutron fluences calculated from literature Ne and Kr isotopic data. Thermal neutron fluence values of them are in agreement with epi-thermal neutron fluences (Hidaka et al., to be submitted). Less

确定了来自阿波罗12和15钻芯的七个月球样品中SM和GD的同位素组成，以讨论在月球表面附近的中子捕获的影响。从A-12和A-15样品的同位素移位计算出的中子通量值分别为（1.77-2.17）X10I D116I D1NCMI D1-2I D1和（3.02-4.68）X10I D116I D116I D1 NCMI D1 NCMI D1-21-2I D1。 εIID2SMIE D2/εiiD2GD2的变化被解释为由于中子能谱的变化。我们的数据表明，中子在下层比上层更热（Hidaka等人，在印刷中）。这种方法用于气象。在五个Enstatite Achondrites（Aubrites）中观察到了源自源自中子捕获效应的εIID1149II D1SM-II D1SM-II D1SM-II D1150II D1SM和εIID1157II D1GD-II D1158II D1GD。这些值晶的同位素变化对应于（1.17-3.99）X10 D116 D1 N CM D1-2 D1的辐照，该中子X10 d116 d1 n cm d1-2 d1在…某些月球样品的估计中性通量值范围内。这些结果表明，aubrites可能位于其母体表面附近，持续数百个MA。此外，从SM和GD同位素系统学（εiD2SMIE D2/εiD2GDIE D2）的组合获得的中子能谱表明，五个aubrites中热中子的能量在200至400 K范围内，并且比A-12和A-15 Lunar Samples（HID）（HID）较低。 SM和GD在八个软骨中的同位素组成显示了软骨中中子捕获作用的证据，对应于（1.03至5.17）x10 x10 d115 d115 d1 d1 n cm d1-2 d1 d1的热中性含量。将八个软骨中四个软骨的四个软骨的SM和GD同位素结果与根据文献NE和KR同位素数据计算出的有关表皮和快速中子的信息进行了比较。它们的热中子通量值与表皮中子的膨胀一致（Hidaka等人要提交）。较少的

项目成果

H.Hidaka et al.: "High fluences of neutrons determined ftom Sm and Gd lstopic compositions in aubrites"Earth and Planetary Science Letters. 173. 41-51 (1999)

H.Hidaka 等人：“中子的高注量由金铜矿中的 Sm 和 Gd 同位素组成决定”，《地球与行星科学快报》。

H. HIDAKA: "Isotopic study of natural fission reactors at Oklo and Bangombe, Gaobn."J. Radioanal, Nucl. Chem., Article. 239. 53-58 (1999)

H. HIDAKA：“Oklo 和 Bangombe、Gaobn 天然裂变反应堆的同位素研究”。

H.Hidaka: "Tc/Ru fractionation in the Oklo and Banombe natural fission reactors,Gabon"Chemistry Geology. 155. 323-333 (1999)

H.Hidaka：“加蓬 Oklo 和 Banombe 天然裂变反应堆中的 Tc/Ru 分馏”化学地质学。

H.Hideka et al.: "High fluences of neutrons determined from Sun and Gd and isotopic compositions in aubrites"Earth and Planetary Science Letters. 173. 41-51 (1999)

H.Hideka 等人：“由太阳和钆确定的中子高注量以及赤铜矿中的同位素组成”《地球与行星科学快报》。

H.Hidaka: "The comparison of neutron energy spectrum between aubrites and lunar soils (A-15) obtained from Sm and Gd isotopic compositions" Meteoritics & Planetary Science. 33. A67 (1998)

H.Hidaka：“从 Sm 和 Gd 同位素组成中获得的赤铁矿和月球土壤 (A-15) 之间的中子能谱比较” Meteoritics