Effective atomic number for Compton scattering: a benchmark tool to characterize materials

Compton scattering is a very useful tool to probe the material properties. Traditional techniques such as energy dispersive spectroscopy (EDS) lead to (i) a choice of small size (amount) of the sample resulting in altering the pristine form of the sample, (ii) an ambiguity while marking the closely lying K-shell and L-shell peaks of different elements. It is felt that this can be overcome through the determination of effective atomic number(Z(eff)) which can yield a fair idea of the content of the material supplementing the EDS information. In the present work, we have made an attempt to determine Z(eff) from Compton scattering with the angles beyond 90 degrees which has an advantage of placing both the radiation source and the detector on the same side of the medium making it possible to analyze the samples such as those of archaeological importance which are usually accessible only from one side. A goniometer assembly using 59.54 keV gamma rays emitted by a 7.4GBq Am-241 isotope and a high purity germanium detector were employed. The values of the Z(eff) have been verified with that of the Auto-Z(eff) program values obtained by making use of the composition information from the EDS data. The present work points to the fact that Z(eff) of archaeological samples is a handy, confirmatory onsite tool for their non-destructive evaluation