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

摘要

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 gamma-rays emitted from a standard ~(241)Am calibration source are due to Compton scattering of gamma-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 ~(241)Am radiation from all surrounding materials except from the targets.An~(241)Am annular source was used to excite the fluorescence radiation.Measurements have been made with a target of parafine loaded with Ce_2O_3 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.