| 摘要 |
PROBLEM TO BE SOLVED: To prevent an excessive current which deteriorates a photomultiplier tube from flowing to the photomultiplier tube without reducing the sensitivity of the photomultiplier tube. SOLUTION: A CPU 14 has a signal prediction part 16 and a comparison/calculation part 18. The signal prediction part 16 predicts the strength of a signal outputted during the next period, based on the strength of a signal from a photodetection unit 10. The comparison/calculation part 18 compares a reference value, which defines the limit value of a current passing through a photomultiplier tube, of the strength of a signal from an A/D converter 12 with a predicted value by the signal prediction part 16, and calculates a voltage applied to the photomultiplier tube 11 so that the strength of a signal during the next period does not exceed the reference value when the predicted value exceeds the reference value. An applied voltage control part 20 is configured to perform applied voltage control, based on an applied voltage value calculated by the comparison/calculation part 18 when the predicted value of the strength of a signal from the photodetection unit 10 during the next period exceeds the reference value. COPYRIGHT: (C)2010,JPO&INPIT
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