A Mass Spectrometer for Photo-Ionization and Microanalysis(I) : Characteristics of Static Operation and Vacuum

概要

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A mass spectrometer for photo-ionization by vacuum ultra-violet light and for microanalysis by static operation was constructed in University of Osaka Prefecture. The analyser tube and ion source can be baked out up to about 400° and 300°C, respectively. The other parts of the mass spectrometer can be baked out at about 130°C. By total 250 hours' baking out and evacuation end vacuum reached to 2×10-9 mmHg, and almost no background peak was detected under dynamic operation by an usual type d. c. amplifier. When static operations were carried out under these experimental conditions, main residual gases of hydrogen, methane and carbon monoxide increased for the duration of static operation. The evacuation rates by the Bayard-Alpert type ionization gauge were measured for hydrogen, methane, carbon monoxide, carbon dioxide, argon, neon and helium. The results indicate that the evacuation rates of hydrogen and methane by the Bayard-Alpert type ionization gauge are considerably large, and that the evacuation rates of noble gases have correlation to their ionization probabilities. The sensitivities in item of A/μcc NTP of noble gases for analysis by static operation were measured, and the results show that the sensitivities(A/μcc NTP)of 40 Ar, 20Ne and 4He are 6.39×10-13, 1.26×10-13 and 6.92×10-14, respectively. Further measurements using a Cu-Be twelve-stage secondary electron multiplier have been continued.