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Monte Carlo Simulation of the X-Ray Fluorescence Spectra from Multielement Homogeneous and Heterogeneous Samples

Published online by Cambridge University Press:  06 March 2019

A. M. Yacout ,
R. P. Gardner  and
K. Verghese
A. M. Yacout
Affiliation:
Center for Engineering Applications of Radioisotopes, North Carolina State University, Raleigh, North Carolina 27695-7909
R. P. Gardner
Affiliation:
Center for Engineering Applications of Radioisotopes, North Carolina State University, Raleigh, North Carolina 27695-7909
K. Verghese
Affiliation:
Center for Engineering Applications of Radioisotopes, North Carolina State University, Raleigh, North Carolina 27695-7909
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Abstract

A Monte Carlo model that predicts the entire photon, spectrum for energy-dispersive X-ray fluorescence (EDXRF) analyzers excited by radio-isotope sources from multielement homogeneous samples is developed and demonstrated. The components of the photon spectrum include: (1) the and Kα and Kβ characteristic primary, secondary and tertiary X rays from both the unscattered and scattered source photons, (2) the characteristic X rays excited by other characteristic X rays that have been scattered, and (3) the scattered source photons from single, double, and multiple scatters in the sample.

The computer code NCSMCXF based on this model has been developed. It is capable of handling up to 20 elements per sample and provides a detailed account of the intensities of the X rays and backscattered source photons per unit source decay as well as a summary of the relative intensities from all elements present in the sample. Cubic splines are used within the code for photoelectric and total scattering cross sections and two-variable cubic splines for angular coherent and incoherent scattering distributions for efficiency in both computation time and storage. The code also provides the pulse-height spectrum of the sample by using the appropriate Si(Li) detector response function. The Monte Carlo predictions for benchmark experimental results on two alloy samples of known composition indicate that the model is very accurate. This approach is capable of replacing most of the experimental work presently required in EDXRF quantitative analysis.

A previous Monte Carlo model that uses the simple assumption of spherical homogeneous particles to approximate sample heterogeneities has been modified to improve the computer execution time requirements for the heterogeneous sample case. A new technique for photon tracking in this medium is used and reduces the computation time requirement by half.

Type
III. XRF Fundamental Parameters and Data Analysis
Information
Advances in X-Ray Analysis , Volume 30: Thirty-Fifth Annual Conference on Applications of X-ray Analysis, August 4-8, 1986 , 1986 , pp. 121 - 132
Copyright
Copyright © International Centre for Diffraction Data 1986

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References

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