| 摘要 |
PURPOSE:To enable an alarm to be generated for each type of all radial rays (alpha, beta, gamma and neutron rays) related to external exposure by separately constituting a neutron ray measurement system, an alpha ray measurement system and a alpha ray measurement system, and arranging the aforesaid systems integrally. CONSTITUTION:A beta ray entrance window 1 has such thickness as not causing the appreciable attenuation of a beta ray, and is positioned in front of a beta ray detection element 2. A gamma ray entrance window 3A allows the passage of only a gamma ray, and is positioned in front of a gamma ray detection element 4. Similarly, another gamma ray entrance window 3 is positioned in front of a radiator 5. When the mixed field of alpha, beta, gamma and neutron rays is considered, the window 1 allows the passage of all radial rays, except for light. In a beta ray detection element 2, however, a material having a reacting sectional area small enough for neutron is used and neutron passes without interaction with the element 2. The neutron in this instance, therefore, does not contribute to the component of an output signal. A gamma ray is directly detected and amplified in the element 2, and counted by a counter 13. A gamma ray detection element 4 is not sensitive to neutron, and detects the gamma ray. This ray is counted by a counter 14. Thermal neutron detector 6 has a radiator 5 at the front thereof and detects even neutron of high energy. This neutron is counted by a counter 15.
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