| 摘要 |
PURPOSE:To obtain fast responsiveness even when the quantity of radiation is extreme ly small by selecting a pulse signal from a pulse generating circuit when the quantity of incident gamma rays is less than a half as much as an overall measurement range or a pulse signal based upon the dosage of incident gamma rays. CONSTITUTION:A semiconductor type gamma-ray detector 12 inputs pulses corresponding to the quantity of incident gamma rays to an amplifying circuit 13. When the quantity of incident gamma rays is less than a half as much as the overall measurement range, a decision circuit 20 connects a switch SW2 to an NOT gate 16 and a switch SW2 to a pulse generator 15, and the pulse signal from the circuit 15 is inputted to a discrimi nating circuit 14. When the quantity of gamma rays is larger than a half as much as the overall measurement range, the switches SW1 and SW2 connect the circuit 13 to the circuit 14. Further, when the quantity of incident gamma rays is small and the pulse signal of the circuit 15 is inputted to the circuit 14, the output of a D/A converter 18 is connected to a differential amplifier 19 through switches SW3 and SW4 and outputted as a signal corresponding to the quantity of gamma rays; when the quantity of gamma rays is larger than a half as much as the overall measurement range, the signal is outputted as it is. Thus, the circuit 14 responds extremely fast even when the quantity of gammarays is extremely small, and the output corresponding to the quantity of gamma rays is obtained.
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