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

通过这个项目，我开发了一个小质量光谱仪，该光谱仪主要用于K-AR日期和生产，与一个商业产品相比，相对较低的成本。机器应该在高等离子分析中有足够的精确度，但不需要高成本，也应该像可能的那样紧凑。为了满足这样的条件，一个阻尼器型质量光谱仪（6厘米半径， 180 °）是计划的，哪个在静态模式下使用。它也是用可移动的机制来满足离子源部分和离子收集器部分的外部，尊重。生产的质量光谱仪显示出一个很好的峰值与一个完整的平坦顶部和一个解决能力约70个峰值的1%山谷。离子源部分和离子收集器部分似乎有效地工作的可移动机制。一个铑丝带被用来制造一种薄膜，使原子离子化。70 V被应用于电离原子的潜力。在正常模式下，一个法拉第笼被用来探测。在当前的发射量为3.2 mA时，对离子源的敏感性估计约为<40>2x 10 ^&lt;-4&gt;A/Torr。为了衡量放射性氩的数量很小，而在低于1 Ma的年龄的基本火山岩中可以看到，敏感性是不够的，无法获得精确的价值。为了克服这种缺陷，一个离子收集器，既有一个Farady-Cage，也有一个二级电子倍增器，已经开发出来。这样一个离子收集器将是有用的，用于测量氩同位素，具有一个宽范围的量子;加上一个微型计算机系统的附加值，就可以通过对质量光谱仪和数据采集和减少系统的控制来完成，因此需要一些附加预算来完成它。

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.