Effects in K X-ray fluorescence spectra due to Compton scattering in the target

In a previous study of our group, it has been shown that broad continua adjacent to the full-energy peaks (the “shoulders”) in the spectra of 59.537 keV γγ-rays emitted from a standard Am241 calibration source are due to Compton scattering of γγ-rays in the source plate (mass of only 0.59 g). An extension of that work is presented with the aim to show that the analogous shoulder spectra also appear in the K X-ray fluorescence spectra, and are due to the Compton scattering of fluorescence radiation in the target. The experimental set-up was carefully designed with the aim to strongly reduce single and double scattering of Am241 radiation from all surrounding materials except from the targets. An Am241 annular source was used to excite the fluorescence radiation. Measurements have been made with a target of parafine loaded with Ce2O3Ce2O3 and, for comparison, with a pure parafine target. To show that Compton scattering is the main cause of the observed shoulder spectra, the measurements were made for three orientations of the targets with respect to the detector-to-target centre-line. The observed changes in the measured spectra clearly show that the shoulders are mainly due to Compton scattering in the targets. Calculations of the shoulder spectra show a good agreement to the measured spectra.