HIGH-ORDER MULTIPLE-SCATTERING CONTRIBUTIONS IN X-RAY SPECTROMETRY

Multiple scattering contributes important parts to the emission spectrum from thick targets excited with x-ray photons. Both the continuous and discrete parts of the spectrum receive enhancement by multiple scattering. Recently, some expressions were deduced in the framework of transport theory allowing the computation of the second-order chains of the Compton and Rayleigh effects. In this work those calculations were extended to the third and the fourth orders of multiple scattering by means of Monte Carlo simulation. Monte Carlo results were computed using full expressions for the angular kernels (i.e. scattering coefficients including atomic form factors). The second-order Monte Carlo result was compared with the computation by deterministic means, showing close agreement except in the extreme of the Compton-Compton spectrum. Higher orders are important for low-Z elements but can be safely neglected in the medium-Z range.