Experimental evaluation of saturation thickness for 662 keV gamma rays in iron at different scattering angle

Abstract

The study of multiple scattering of gamma photons is considered as an important tool for the correct determination of electronic momentum distribution in an atom, non-destructive testing, effective atomic number of composite materials, reactor shielding etc. A collimated beam from 137Cs radioactive source of strength 0.222 TBq emitting 662 keV gamma rays is allowed to impinge on cylindrical targets of iron with varying thickness. The scattered photons are detected by a properly shielded NaI(Tl) scintillation detector, having dimensions 51 mm x 51 mm diameter and thickness respectively, placed at different scattering angles. It is observed that the number of multiply scattered photons increases with increase in target thickness and saturate for a particular thickness called saturation thickness. The Multiple scatter fraction (MSF) increases with the increase of scattering angle at various energy window widths for iron targets. The same experiment is repeated with an HPGe gamma detector at scattering angle 90° and found the same value of saturation thickness. The Monte Carlo calculations based upon the package developed by Bauer and Pattison (1981) support the present experimental results.