DEVELOPMENT OF THE COMPLETE SPECTRAL RESPONSE APPROACH TO ENERGY DISPERSIVE X-RAY FLUORESCENCE

A technique is demonstrated to predict the entire pulse-height spectrum for EDXRF systems that consist of an annular ring photon exciting source, a coaxially positioned right circular sample, and a circular Si(Li) detector. Photon spectra are generated with Monte Carlo models that can be combined with a Si(Li) detector response function to predict pulse-height spectra as a function of sample composition for both homogeneous and heterogeneous samples.;The Monte Carlo models have been developed to simulate the response of three different types of samples: (1) homogeneous samples, (2) heterogeneous particle samples where the particles may be treated as spheres composed of a homogeneous mixture of all the elements in the sample, and (3) heterogeneous particle samples where each particle may be treated as a sphere composed of a pure element. For the case of homogeneous samples, a technique for performing an elemental analysis using only the predicted responses from the model is demonstrated.;The detector response function is treated as a probability distribution function. Nonlinear least-squares techniques have been developed to determine the parameters for the derived response function over a range of energies by using spectra from pure element samples. The response function is easily discretized for application to typical multichannel analyzer spectra with channels of constant energy width.