Variation of S/N ratio with target thickness for pure Z materials using back-scattering of gamma photons

摘要

The variation of signal-to-noise ratio (S/N ratio) with thickness of pure Z materials (6≤Z≤50) is calculated for back-scattering of gamma photons, by employing an 3" × 3" NaI(Tl) scintillation detector. In order to have maximum back-scattered photons, detector is placed in back-scattering geometry without any collimation. Experimentally, it has been seen that numbers of multiply back-scattered photons increases with increase in target thickness and gets saturated at a particular depth called saturation depth. The detail of this study helps in Compton profile measurements as singly and multiply back-scattered gamma photons corresponds to signal and noise in it. It is concluded that signal-to-noise (S/N) ratio decreases with increase in thickness of the target as well as with increase in atomic number. Efficiency of 3" × 3" NaI(Tl) scintillation detector is corrected by making use of Response function on the recorded pulse-height distribution in order to have an increment in accuracy of experimental results. Monte Carlo calculations also support the present experimental results.