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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，我已经开发了一个小型质谱仪，主要用于K-Ar定年，并与商业相比，成本相对较低。为了满足精确K-Ar定年所需的Ar同位素分析精度，该仪器应具有足够的精度，但不要求高的成本，并应尽可能地紧凑，为此，我们设计了一台Dempster型质谱计（半径6cm，180 μ m），它是静态工作的。研制的质谱仪峰形良好，峰形平坦，在峰谷1%处的分辨力约为70。离子源部分和离子收集器部分的可移动机构似乎有效地工作。一个带状物被用来作为灯丝来激发一个原子。70 V作为电势施加到原子上。在正常模式下，法拉第笼用于检测离子。在发射电流为3.2mA时，获得的离子源灵敏度<40>约为2 × 10 ~（-1）<-4>A/Torr。对于年龄小于1 Ma的基性火山岩中微量的放射成因Ar的测量，灵敏度不足以获得精确的值。为了克服这种缺陷，已经开发了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各种氩量的氩同位素，加上微机系统，通过控制质谱仪和数据采集与处理系统，可进行更精确的分析，但需增加经费。