Study on α ray measurement and calibration of soil samples

For total alpha measuring of soil samples, we use thick source method. After calibration of the instrument, we measure the samples. Through analysis on composition of the soil sample, we choose two calibration sources to calibrate the instrument (Low Background α and β measuring device) respectively-source of ²⁴¹Am and numbers for GBWO4127 standard materials (natural uranium and thorium ore). 9 standard materials was used to simulate the soil samples. By comparison of the data, it was found that for mixed source samples, the result of using CBWO4127 source as calibration source is more exact than ²⁴¹Am, the error from 20% to 40% decrease to 20%. For other standard samples, the errors are not improved, most of them have increased. Because its components has a large gap with real soil. The soil is not only composed of a single contains U, Th or K ingredients. Because mixed source sample is closer to the real soil ingredients, and more suitable for the soil sample. Therefore, for total alpha measuring of soil samples, CBWO4127 standard materials (natural uranium and thorium ore) was recommended as calibration source. (authors)