Developmental Research of mass spectrometric system for laser probe dating of mineral

我们设计和建造了一台用于惰性气体分析的超高灵敏度低本底质谱计及其配套系统，并进行了试验分析。该系统已在京都第29届国际地质大会上提出。该质谱系统具有三个收集器，可以同时分析三种氩同位素，与现有的单收集器系统相比，具有极高的同位素分析精度，是年轻火山岩定年的有力工具。不幸的是，MS中的离子枪在最后一年的中期发生了一些故障，使得现在无法准确地分析天然样品。我们要求Ayumi工业公司改进离子枪和重建，直到项目结束时，我们才完成了完美的系统，但并不认为这个项目是失败的，因为我们已经掌握了这个质谱系统的基本能力。我们认为这是世界上第一台惰性气体分析用的三重收集器质谱计，我们用现有的质谱计解决了天然岩矿氩分析的基本问题，并将建立的分析技术应用于地质材料。大量的结果已发表在许多文献中。我们还研制了激光探针抽氩系统，用于微量材料或细晶粒单晶的Ar-Ar定年。这使得从几微克的材料中检测出氩成为可能，并在500 ~ 1500 ℃的分段加热中以± 1 ℃的相对精度控制材料的温度。这也适用于单晶激光探针Ar-Ar定年和寄主岩石热历史的研究。它的精确度可能是世界上最好的。

We have designed and constructed new mass spectrometer and the associated system with ultra high sensitivity and low background for noble gas analysis, and then proceeded the test analysis. This system has been presented at 29th Internatinal Geological Congress in Kyoto. This mass spectrometric system having three collectors has made it possible to analyze simultaneously three argon isotopes and has extremely high precision for the isotopic analysis in comparison with the present system with single collector, being powerful for dating young volcanic rocks. Unfortunately, the ion gun in MS Happened to have some troubles in middle of the final research year, making it imposible to analyze exactly natural samples now. We have required the improvement of ion gun and the rebuilding by Ayumi Industry Co., Ltd. We were not able to complete the perfect system until end of the term of project but do not think this project unsuccessful because we have already catched the basic ability of this mass spectrometric system before the trouble. We believe this is the first mass spectrometer with triple collector system for noble gas analysis in the world.We have sexamined the basic problem of argon analysis of natural rocks and minerals using the present mass spectrometer and applied the established analytical technique to geological materials. The lots of results have been published in many literatures. We have also developed laser probe argon extraction system for very small aount of materials or fine grained single crystal for Ar-Ar dating. This has made it possible to detect argon from the materials of few micro gram and control temperatures of the materials with a relative accurracy of +-1ﾟC between 500 and 1500ﾟC in the stepwise heating. This is also applicable to laser probe Ar-Ar dating of single crystal and examination of thermal history of the host rock. Its precision is probably the best in the world.