where (l/q) is mass attenuation coefficient (cm2/g), q and v are the
density (cm3/g) and the thickness of the sample (cm). The higher
the (l/q) value, the less energy passes through the material. In this
paper, we also introduce the half value thickness (HVT) to characterize
radiation shielding property directly. The HVT equals the
thickness of a sample when the intensity of the transmission beam
I was attenuated to half of the intensity of the incoming beam I0.