| 摘要 |
PURPOSE:To simplify the title instrument by comparing the output of a crest value extracting circuit with a prescribed value and controlling a gain so that their deviation is zero. CONSTITUTION:The CO (capacitor) 103 of an upper envelope detecting circuit is charged up to the crest voltage of pulses due to a reference signal (a) from an amplifier 5. Charges in the CO 103 are discharged through a charging resistance 104 and the charging voltage is updated with the pulse of a next signal (a). Consequently, the voltage history of the terminal voltage of the CO 103 becomes a saw-tooth waveform having an envelope based upon the upper side of a reference signal corresponding pulse train. This saw-tooth waveform voltage is inputted to a lower envelope circuit and a CO 107 is charged up to the minimum voltage value of the upper envelope waveform voltage (b). The CO 107 is charged to the positive potential side through a discharging resistance 108 and the charging voltage is updated with the minimum voltage value of a next voltage (b). Therefore, the voltage history of the terminal voltage across the CO 107 becomes the lower envelope waveform of the voltage (b). This lower envelope waveform voltage (c) is compared 11 with a constant set voltage and the output of a power source 9 is controlled in a zero direction with the difference voltage, so that the gain of a photomultiplier 3 is held constant.
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