An Attempt for the Precise Isotope Analysis: Modification of a Compact Type Mass Spectrometer.

概要

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A compact virtual image double focusing mass spectrometer was adopted for the precise isotope analysis with surface ionization ion source. A interface with 16-bit DA converter was set into the computer for automatic control of magnetic field. This new system enabled to measure isotopic ratios by peak hopping method. To obtain high precision, the digital voltmeter under computer control was introduced for collecting data and processing them successively.The flatness of the peak top and the stability of the magnetic field during the single run were checked and found to be satisfactory. For the test of the measuring system, the isotopic ratios of K, Rb and Sr were measured using shelf reagents. It was concluded that (1) by the Faraday collector, the isotopic ratio could be measured with the precision better than 0.01% when the ion currents for both isotopes were higher than 10-11A, (2) for the isotope less abundant than 10-4, the precision achieved a few percent by Faraday collector with ion current of 10-15A, while the precision was within 1% by SEM collector with ion current of 10-17A. The performance of the mass spectrometer was found to be satisfactory to measure isotopic ratios with a high precision.
日本質量分析学会の論文