Simultaneous measurement of argon isotopes using microchannel plates

点击翻译按钮获取中文摘要

In 40Ar/39Ar stepwise heating experiments, the fast measurements need to be carried out to obtain time-independent data sets, in particular for small samples. In this study, microchannel plates are used for ion detection, and simultaneous measurement of five argon isotopes from 36Ar to 40Ar was attempted.Simple combination of microchannel plates and a position sensitive detector is not suitable in an ultrahigh vacuum system because it needs baking at temperature over 100℃. Thus, we adopted the two dimensional Modified Backgammon method with Weighted coupling Capacitors(MBWC) designed by Drs Mizokawa at Wakayama College of Technology and Shiromaru at Tokyo Metropolitan University.36Ar,38Ar and 40Ar from atmosphere were detected simultaneously, but the system was not enough for quantitative measurements. The large volume of 40Ar disturbs the simultaneous measurement of 36Ar and 38AT signals which is approximately one three hundredth and one sixteen hundredth, respectively. The system allows two dimensional ion detection, and it is effective to adjust ion optics of each isotope in a mass spectrometer.Designing an one-dimensional chain of linear channeltron was considered to make quantitative measurements, and it became possible with coorperation with Dune Inc. Combining the two dimensional system and a small mass spectrometer with one dimensional system allow easy tuning of ion optics and highly sensitive quantitative argon mass spectrometry. Independent developments of two different types of mass spectromenters is now resulting in a new ultra small highly sensitive mass spectrometer.Signals from the position sensitive detector is measured by the ion counting method. The interface and program were developed as well as the automatic control for the measurement. The control and measurement units are connected via LAN cable. The extraction and purification system to separate ultra low volumes of the standard air and high purity gases were completed.