Research on the origin of micrometeorite by extremely accurate instrumental neutron activation analysis

本研究的第一个目的是建立超小型微陨石样品中多元素的精确中子活化分析技术（INAA）。二是积累化学数据，以便精确地讨论宇宙尘埃的起源。超小型微陨石样品仪器中子活化分析快速处理方法的研制。颈眼无法看到直径小于100 μm的微小样品。采用高纯度聚乙烯（3x3 mm）袋装微量样品，建立了INAA快速处理系统。同时，研制了新型长半衰期核素INAA小样品辐照容器。亲石元素（如稀土元素）的玻璃标准是由标准岩粉（如JB-1）制成的。采用高纯度金属制备了亲铁元素（Au、Ir等）的合金标准。检查这些标准品在10 ~ 100 μg范围内的均质性。然而，与微陨石样品的放射性活动相比，合金标准的放射性活动过高。从南极富士圆顶站生活水箱的沉积物中收集的微陨石样本由INAA.4进行了分析。对从南极大和裸冰原收集的未融化微陨石样本进行了初步分析。

The first purpose of this research is establishment of accurate analytical technique for multi-elements by instrumental neutron activation analysis (INAA) for multi-elements in ultra-small micrometeorite sample. The second is accumulate of chemical data for precise discussion of the origin of cosmic dust.1. Development of the rapid handling method of instrumental neutron activation analysis for ultra-small micrometeorite sample. We cannot see tiny sample such diameter as less than 100 μm with the necked eye. By using the high purity polyethylene bag (3x3 mm) which enclosed tiny samples, a rapid handling system of INAA is established. New irradiation container of tiny sample for INAA using long half life nuclides was also developed.2. Glass standards for lithophile elements such as rare earth elements were made from standard rock power (e.g. JB-1). An alloy standard for siderophile elements (Au, Ir etc) was made from high purity metals.Homogeneities for 10 to 100 μg range of these standards were checked. However, radio activity of alloy standard was too high compared with the radio activities for micrometeorite samples.3. Micrometeorite samples collected from sediments in the water tank for living at the Dome Fuji station, Antarctica were analyzed by INAA.4. Preliminary analyses were performed to unmelted micrometeorite samples collected from Yamato bare ice field, Antarctica.