An Ion Counting Method with Multichannel Pulse Height Analyser for High Sensitive Mass Spectrometry

概要

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A newly developed ion counting method in mass spectrometry is described. This method makes use of analog switch, so as to make the output pulse height from the secondary electron multiplier linear in (m/e)^<1/2> of the ions. When fed to a multichannel pulse height analyser (MC-PHA), these output pulses produce a histogram which directly represents the mass spectrum. The new method makes possible a rapid scanning of the magnetic field in a mass-spectrometer. In order to overcome problems of counting loss of ions, which is caused mainly by MCPHA, it is required to change the accumulation rate of pulses in MCPHA especially for the most abundant isotopes. For this purpose, we designed a "window sensitivity attenuator", in which the incoming rate of ions to the electron multiplier is converted into its 1/2^n by using a series of binary counters. The new counting method was applied to the isotopic measurement on magnesium with samples of inclusions of the Allende Meteorite, and the results are presented.
社団法人応用物理学会の論文
1975-09-05