| 摘要 |
PURPOSE:To enhance the reliability of measurement, by providing a vacuum degree detection means and a control means for controlling the start and stop of the measurement so as to presume, from the degree of vacuum in a vacuum chamber, the time at which the quantity of produced parent ions increases, and to surely detect parent ions. CONSTITUTION:A vaccum degree detection means 4 for detecting the degree of vacuum in a vacuum chamber 1 including an ion source section 2, and a control means 9, 10 for controlling the start and stop of measurement depending on the degree of vacuum are provided. A degree of vacuum at the start of the measurement and a degree of vacuum at the end of the measurement are preset according to a time zone in which the quantity of produced ions peaks. Signals indicating the degree of vacuum at the start of the measurement and that of vacuum at the end thereof are sent out from a measurement start/stop vacuum degree setting circuit 9. A comparator 10 compares the signals with a signal indicating the actual degree of vacuum and sent out from a vacuum degree measurement circuit 8, and a mass spectrum is measured by a mass spectrum measuring circuit 11 in accordance with a measurement control signal. The measurement can thus be performed at the best timing on the basis of the detected degree of vacuum, then the parent ions can be detected surely to enhance the reliability of the measurement.
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