Figure 3. the mean spectra at different test positions
Figure 4. the total counts of the spectra at different test positions
From figure 3, we noticed that the characteristic peak of Cs-137 located at the channels between 240 and 290. The difference between background spectra and source contained spectra became obvious until the 100-s mean spectra were acquired. From figure 4, due to the statistic fluctuations, the total counts of source contained spectra and background spectra were located in overlap range, especially the source contained spectra were collected at the low-dose rate positions. Therefore, it is hard to discern them based on the total counts. Figure 7 showed typical 1-s spectra at different test positions.