Monte Carlo Simulation of Secondary Fluorescence in Small Particles and at Phase Boundaries

Abstract.

 Results from Monte Carlo simulations and experimental measurements of X-ray spectra of small Cu-particles in Fe-containing slags are presented. The analyzed Cu-particles remain suspended in flash smelting and Cu converter slags, which contain Fe up to about 33 wt%, and have diameters ranging from 5 up to 100 μm. Conventional standardless analysis of measured X-ray spectra gives an apparent Fe content of ∼ 1–5 wt%, depending on the particle diameter, which cannot be explained in terms of the thermodynamic solubility of Fe in solid Cu. In order to study the influence of the Fe-containing slag to the apparent Fe content in the particles, X-ray spectra have been computed by means of Monte Carlo simulation of the coupled electron and photon transport. The simulation code used is largely based on the general-purpose simulation package PENELOPE and it incorporates ionization cross sections evaluated from an optical-data model and bremsstrahlung cross sections that reproduce radiative stopping power derived from partial wave calculations. Simulated Fe k-ratios, for different experimental situations, have been found to be in satisfactory agreement with measurements. The apparent Fe content is explained in terms of secondary fluorescence of Fe Kα by Cu Kα X-rays.