Noble-gas mass-spectrometer of high performance

由于惰性气体在化学上是惰性的，并且它们的化学性质相似，我们可以把它们理解为具有23种同位素的化学元素，在宇宙化学和地球化学中。此外，还有由不同寿命的放射性母核素产生的稀有气体同位素。这使我们能够将惰性气体应用于有关地球和行星系统演化的问题。为了同时了解陨石稀有气体的同位素特征和捕获位置，我们用激光微探针对陨石样品进行了分析。为了测量10^4原子以下的惰性气体，我们制作了一个QQQH场配置的质谱计。该光谱仪具有低倍率和三维聚焦。我们考察了该光谱仪的灵敏度、质量分辨率和本底（真空）。虽然获得了良好的灵敏度，但在质量分辨率和背景光谱方面还存在一些问题需要解决。

Since noble gases are chemically inert and similar in their chemical properties, we may grasp them as a chemical element with 23 isotopes, in cosmo-and geo-chemistry. In addition, there are noble gas isotopes produced from radioactive parent nuclides of different lifetime. These enable us to apply noble gases to problems concerning the evolution of the earth and planetary system. To know isotope signatures and trapping sites of meteoritic noble gases simultaneously, we analyze meteorite samples with a laser-micro-probe. For measuring noble gases of 10^4 atoms or less, evolved with the laser-micro-probe, we made a mass spectrometer of QQQH field configuration. The spectrometer has low magnification and three-dimensional focusing. We investgated sensitivity, mass resolution and background (vacuum) of the spectrometer. We obtained a good sensitivity but there remain some problems to be solved in mass resolution and background spectrum.