Improved Rayleigh to Compton scattering ratio curves for mass attenuation coefficients determination for X-ray fluorescence analysis.

Nondestructive assays are essentials for certain types of sample materials, and, among those, the X-ray fluorescence technique enables the determinations of stable elements, and there is an increasing effort on the development of equipment to suit the various needs. Nevertheless, a great difficulty on the analysis of unknown materials' composition is to account for self-absorption of the fluorescence photons that must be considered in the elemental concentration calculation. The correlation between the Rayleigh to Compton scattering ratio to the mass attenuation coefficient has proved to follow a single polynomial function for the first 20 elements of the periodical table with a correlation factor higher than of 0.998 for the sixth order function. The Rayleigh to Compton scattering ratios for pure elements and the 22.16 keV photons, the main energy from an X-ray tube with silver anode, were determined with the MCNP6 Monte Carlo computer code. Two scattering angles were considered. Reference samples were measured, and the calculated results were compared to the literature values of the mass attenuation coefficient for some known samples and showed to be within 20% for de 90° scattering angle. Only Lucite was slightly above 20%. Curve fit coefficients are also presented for the 7.11- and 17.40-keV photon energies. [ABSTRACT FROM AUTHOR]