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Development of a small mass spectrometer for K-Ar dating with a low-cost

低成本小型 K-Ar 定年质谱仪的研制

基本信息

批准号：
62840026
负责人：
KANEOKA Ichiro
金额：
$ 7.36万
依托单位：
Earthquake Research Institute, University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research
财政年份：
1987
资助国家：
日本
起止时间：
1987 至 1988
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-62840026/
关键词：
K-Ar dating Small mass spectrometer Ar isotope analyses Movable mechanisms for the ion-source part and the collecotor part イオン・コレクター移動機構二次電子増倍管 K-Ar代測定イオン源感度

项目摘要

Through this project, i have developed a small mass spectrometer which is mainly used for K-Ar dating and produced with a relatively low-cost in comparison with a commercial one. The machine should have a sufficient precision in Ar isotope analyses for precise K-Ar dating, but it does not require high cost and should be compact as much as possible.To fulfil such conditions, a Dempster-type mass spectrometer(6cm radius, 180゜) wa planned, which is used in static mode. It is also equipped with movable mechanisms for the ion-source part and the ion-collector part from the outside, respectively.The produceed mass spectrometer shows a good peak shap with a complete flat-top and a resolving power of about 70 at 1% valley of the peak. The movable mechanisms for the ion-source part and the ion-collector part seem to work effectively. A rhenium ribbon is used for the filament to ionize an atom. 70V is applied as the potential to ionize an atom. In a normal mode, a Farady-cage is used to detect ions. With the emission current of 3.2mA, the obtained sensivity for the ion-source is_<40> estimated to be about 2x10^<-4>A/Torr. To measure very small amount of radiogenic Ar as is observed in basic volcanic rocks with an age of less than 1Ma, the sensitivity is not sufficient enough to get precise values. To overcome this defficiency, an ion collector with both a Farady-cage and a secondary electron multiplier has been developed. Such an ion-collector would be useful for measuring Ar isotopes with a wide range of ar quantity.With the addition of a micro-computer system, more precise analyses will be made thorugh the controlling of the mass spectrometer and the data acqusition and reduction systems, though some addidional budget is required to purdhase it.

通过这个项目，我开发了一个小型质谱仪，主要用于K-Ar测年，与商用质谱仪相比，生产成本相对较低。这台机器在进行精确的K-Ar测年的Ar同位素分析时应该有足够的精度，但它不需要高成本，并且应该尽可能地紧凑。为了满足这些条件，我们计划了一台dempster型质谱仪（6cm半径，180），用于静态模式。所述离子源部分和离子收集器部分从外部分别设有可移动机构。所制备的质谱仪具有良好的峰形，完全平顶，在峰谷1%处的分辨能力约为70。离子源部分和离子收集器部分的可移动机构似乎工作有效。铼带用于灯丝使原子电离。施加70V作为电离原子的电势。在正常模式下，法拉第笼被用来检测离子。在发射电流为3.2mA时，离子源的灵敏度约为2 × 10^<-4>A/Torr。对于年龄小于1Ma的基性火山岩中观测到的极少量放射性成因氩，其灵敏度不足以得到精确的数值。为了克服这一缺陷，开发了一种具有法拉第笼和二次电子倍增器的离子收集器。这种离子收集器可用于测量Ar量范围大的Ar同位素。随着微型计算机系统的增加，将通过控制质谱仪和数据采集和还原系统进行更精确的分析，尽管需要额外的预算来购买它。