The obtained data is used to draw Gaussian plots for each angle in order to determine the photopeaks. Figure 4 shows the Gaussian plot of the data gathered from the Cs-131 at 30 degree of scattering angle. Note that there are 3 peaks in the graph. From left to right, the identified peaks are: low energy radiation, back scattering, and the photopeak located around channel 400. The table of photopeaks are shown in figure 5 along with the peak count, the number of events in the peak of the Gaussian. The range of the Gaussian is determined to be the value of the count that are half that of the peak value, the standard deviation. However, the peak count cannot be considered the yield value without correcting the value for the efficiency of the detector which varies depending on the scattering angle.