plane by a 2″2″NaI(Tl) detector having an energy resolution of 8%
at 662 keV (BICRON model 2M2/2) equipped with CANBERRA
photomultiplier tube base model 802-5. The optimize distance
between the source and the scatterer was set to 20 cm and 20 cm
between the scatterer to the detector. The spectra were recorded
using a CANBERRA PC-based multi-channel analyzer (MCA). The
spectrum on the MCA of detector give instance counts for each of
1024 bins divided by voltage. The angle of the scatter detector (θ)
was adjusted to produce the different gamma rays energies and
acquiring measurements on the MCA. The accuracy of scattered
energy was reported in literatures (Limkitjaroenporn et al., 2013,
2013).