An Experimental Study of Energy Dependence of Saturation Thickness of Multiply Scattered Gamma Rays

The possibility of a photon being scattered more than once may be significant for a rectangular sample having a finite depth and lateral dimensions. The current evaluation is carried out to study about the energy and intensity distributions of 279, 662 and 1120 keV gamma rays multiply scattered from rectangular samples of copper, iron and zinc having different thickness at a scattering angle of 90°. The scattered photons are detected by a 51 mmx51 mm NaI(Tl) scintillation detector whose detector response unraveling, transforming the pulse-height distribution to a photon energy spectrum, is attained with the help of 10x10 inverse response matrix. By applying the self-absorption correction in the sample, there is enhancement in the number of multiply scattered photons, while the saturation thickness remaining unchanged. When the same experiment is repeated with HPGe gamma detector, saturation thickness remains unaltered. We perceive that with increment in the incident gamma photon energy, the saturation thickness also increases. The signal-to-noise [1] ratio is found to be decreasing with increase in the sample thickness. Monte Carlo calculations based upon the package described by Bauer and Pattison [2] support the current experimental results.