The automatic control system using a personal computer for noble gas mass spectroscopy.

Igarashi George, Ozima Minoru

doi:10.5702/massspec.35.258

We have developed an automatic control system using a personal computer (PC9801, NEC Co.) for noble gas mass spectrometric analyses. We have analyzed successfully elemental and isotopic abundances of heavy noble gases (Ne, Ar, Kr and Xe) in terrestrial gas and water samples such as volcanic gas, deep seawater and lake water samples with this system.<br>The magnetic field is measured with a Hall-probe Gauss meter and is automatically controlled by the personal computer. Ion beam is detected by a vibrating reed electrometer with a SEM. The current is read in the personal computer and the ampere range of the electrometer is also automatically controlled by the computer.<br>We have developed a software (in N88 DISK BASIC) for noble gas analyses using this system. We took full advantage of the “color graphics” and “interrupt operations” of the PC 9801 personal computer. We provide two kinds of scan programs: one is to monitor mass spectra on the color display and the other is to correct peak positions and to calculate resolution of the mass spectrometer. Mass spectrometric data of noble gas isotopes are obtained by a combination of peak scan and peak hopping, that is, only a top part of a peak (about a half of the peak width) is scanned and the 10 running means are calculated, and then the magnetic field is hopped to the next peak. The data are stored in a floppy disk. A time extrapolation of the data to the time when the sample was introduced into the mass spectrometer is carried out by least-squares fitting with either a linear or an exponential function. A weighted mean of the data is also calculated for comparison.

The automatic control system using a personal computer for noble gas mass spectroscopy.

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