In addition to the large Al scatterer, a smaller Al scatterer is placed between the source and the detector. The scattering angle is set to 25 degrees and 45 degrees. The same measurement is also made for copper scatterer of the same size. The ratio of the area of the photopeaks between these two cylinders (Copper to Aluminum) are 1:1.03 for 25 degrees and 1:0.599 for 45 degrees, respectively. Considering that the mass absorption coefficient ratio is 0.974 at 0.662 MeV and 0.952 at 0.55 MeV, the ratio for copper to aluminum cylinder is 1:1.004 for 25 degree and 1:0.57 at 45 degree.
Theoretical Model
According to the Compton scattering equation, the energy transmitted by the scatterer can be expressed as a linear equation,