Applicability of annular‐source excited systems in quantitative XRF analysis

Abstract

AbstractRadioisotope‐excited XRF systems, using annular sources, are widely used in view of their simplicity, wide availability, relatively low price for the complete system and good overall performance with respect to accuracy and detection limits. However, some problems arise when the use of fundamental‐parameter techniques for quantitative analysis is attempted. These problems are due to the fact that the systems operate with large solid angles for incoming and emerging radiation, and both the incident and take‐off angles are not trivial. In this paper, an improved way to calculate ‘effective’ values for the incident and take‐off angles, using Monte Carlo (MC) integration techniques, is shown. In addition, a study of the applicability of the ‘;effective’ angles for analysing different samples, or standards, was carried out. The MC method allows also calculation of the excitation‐detection efficiency for different parts of the sample and estimation of the overall efficiency of a source‐excited XRF set‐up. The former information is useful in the design of optimized XRF set‐ups and prediction of the response of inhomogeneous samples. A study of the sensitivity of the results due to sample characteristics and a comparison of the results with experimentally determined values for incident and take‐off angles is also presented. A flexible and user‐friendly computer program was developed in order to perform efficiently the lengthy calculations involved.