| 摘要 |
A plastic scintillation detector (14) generates on the basis of ionizing radiation coming from a radiation source (16) light flashes which are converted by a photoelectric transducer (20), for example a photoelectron multiplier, to electrical output pulses. An evaluation circuit (22) counts the output pulses as a measure of the radiation intensity. For automatic stabilization of the scintillation detector a light source (24) is controlled by a driving circuit (26) in such a manner that it transmits light pulses whose intensity is modulated in accordance with a predetermined periodic function, for example a sawtooth function. The modulated light pulses are also intercepted by the photoelectric transducer (20) and converted by the latter into electrical reference pulses. A monitoring circuit (28) determines in each modulation period the number of reference pulses whose amplitude exceeds a predetermined reference threshold value lying in the modulation interval. The pulse number determined is used to stabilize the scintillation detector, either by controlling the amplification in the sense of maintaining a predetermined pulse number or by corresponding correction of the measurement result furnished by the evaluation circuit. |
