| 摘要 |
PURPOSE:To measure the amount of RI (radioactive isotope) at a specific place only by a thin shield body without any of noises due to the RI at the place by using a thin detecting element which has high sensitivity to beta rays and low sensitivity to gamma rays. CONSTITUTION:The thin semiconductor detecting element which has high sensitivity to beta rays and low sensitivity to gamma rays is provided in a case 2 which is closed at one end with thin foil 3 and the beta rays which are incident through the foil 3 are detected. The foil 3 impedes the incidence of the beta rays and is so thin as to prevent light from entering the case, and this foil uses, for example, aluminum foil, resin film, etc. Then, liquid which contains a beta-ray source accumulated in a container 5 runs through a tube 6 in front of the foil 3. The shield body 7 made of a lead plate, etc., having enough thickness to cut off the beta rays is provided as a shield mechanism between the container 5 and element 1, so even when the amount of RI in the tube 6 is smaller than that in the container 5, there is no hindrance to measurement.
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