The spectrum on the MCA of detector gave instance counts in
each of 1024 bins divided by voltage. To measure the angular
dependence of Compton scattering, we first perform a calibration
relating the channel number of the MCA spectrum to the energy
of known gamma-ray sources and vary the angle of the scatter
detector and acquire measurements on the MCA. The different angles
(h) were used to produce the different gamma ray energies.
Kaewkhao et al. (2012) first applied the Compton scattering technique
to mass attenuation coefficient measurement, and the validity
of Compton scattering system and energy calibration have been
confirmed.
To measure mass attenuation coefficients, the sample was
placed between the scattering rod and detector (Fig. 1). The intensities
of scattered photon (before traveling through the sample)
were detected as incident photon intensities (I0). After the photon
traveled through the sample, the attenuated photon intensities (I)
were detected, and Eq. (2) was used to determine mass attenuation
coefficients.
The statistical error of gamma ray energies in this experiment
calculated from full width at half maximum (FWHM) of the full
energy peak. The width of a Gaussian distribution is related to
the standard deviation r by (Trousfanidis, 1983).