An application of the environmental radiation detector to scientific education

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We developed the alpha-ray detector (for natural radio active substance) until 1992. The sensor is P.I.N. photo diode. This device is safely to treat, because it works by connecting a domestic outlet and dry batteries. It costs less than 100,000 yen to make the detector. Electric circuit is simple so that senior high school students can understand it easily.By this detector, We measured energy spectrum, which is shown in Fig.1, of alpha-rays emitted from ^<218>Po:6.0MeV and ^<214>Po:7.7MeV of daughter nuclei of ^<222>Rn, which is evaporated from well water(8 liter,20ﾟC). The energy resolution is about 80keV. In this case, the time series analysis of alpha-ray (^<218>Po and ^<214>Po) counting rate is shown in Fig.2 as a solid line. A peak value is 120*25 (counts/hour). We can show another time series data as a dotted line in Fig.2. This curve comes from a measurement by using water from water supply (8 liter, 20ﾟC) on the same condition. This case shows us a little bit of low counting rate.We corporate with four high school teachers about educational practice through the data taking and analysis.