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应用一个大体积的NaI(T1)探测系统,用试验方法研究了钾、铀、钍的谱随离地面高度的变化。用胶合板屏蔽模型,以模拟γ辐射在空气中的吸收。用这种方法在大型放射性混凝土标定模型上测得了γ谱的形状。数据的数学分析表明,在试验范围内(0-112m空气),三种放射性元素中每一个谱实质上是由两个成分组成的,其比例随探测器和源之间吸收物质的量而变化。据此可以看出,所有有关源-探测器的距离以及源含量的基本信息都可以从航空γ能谱中获得。
A large volume NaI (T1) detection system was used to study the changes of the spectra of potassium, uranium and thorium with the height of the ground by experimental methods. The model is shielded with plywood to simulate the absorption of gamma radiation in the air. In this way, the shape of the gamma spectrum was measured on a large scale radioactive concrete calibration model. Mathematical analysis of the data shows that within the experimental range (0-112 m of air), each of the three radioactive elements consists essentially of two components, the ratio of which varies with the amount of substance absorbed between the detector and the source . From this we can see that all the basic information about the source-detector distance and source content can be obtained from the aerial gamma spectrum.