Measurement of the effective atomic number of composite materials using Rayleigh to Compton scattering of 279 keV gamma rays

In the present work, to determine the effective atomic number of composite materials of known composition such as brass, bronze, soldering material, perspex and bakelite, the scattering of 279 keV γ-rays is studied using a high-resolution HPGe (high purity germanium) semiconductor detector placed at 50° to the incident beam. The experiment is performed on various elements with atomic number satisfying, 13 ≤Z ≤ 79, for 279 keV incident photons. The intensity ratio of Rayleigh to Compton scattered peaks, corrected for photo-peak efficiency of the γ detector and absorption of photons in the target and air, is plotted as a function of atomic number and constitutes a fit curve. From this fit curve, the respective effective atomic numbers of the composite materials are determined. The agreement of measured values of the effective atomic number with the theoretical calculations is found to be quite satisfactory. Copyright © 2007 The Royal Swedish Academy of Sciences.