Improvements in standardless calibration procedures for micro-XRF

SOSA, C.; SBARATO, V.; DEL LAMA, L.S.; POLETTI, M.; PEREZ, R.D.

Michigan

Simposio; Symposium on Radiation Measurements and Applications (SORMA XV); 2014

The XRF emission from a bulk sample has not a linear dependence with elemental concentrations because of the so called matrix eects. The most versatile approach to correct matrix eects consists of the application of the Fundamental Parameter method (FP) which requires few calibration standards for the quantication of a wide range of matrices. For FP, the physical processes in the sample leading to the XRF emission are described by a set of analytical equations. It requires a database of fundamental parameters and the spectral distribution of the excitation radiation as well. For the Microanalysis by XRF (micro-XRF), the high intensity and anisotropy of the photon ux at the output of the focalization lens dicult a direct determination of the emergent spectrum. Dierent techniques have been used in the past to estimate the excitation spectrum using indirect measurements, such as attenuation of the primary intensity, x-ray scattering and induced x-ray uorescence in targets. The first two methods are based on approximated theoretical models which produces limitations in accuracy. The induced x-ray fuorescence in targets technique consists of the measurement of the x-ray fluorescence intensity from several thick targets covering the emission energy interval of the x-ray source. The method has the advantage that it not requires approximations or any assumption about the physical characteristics of the x-ray source keeping the accuracy less than 10%. A drawback is that the result of the method is the cumulative spectral distribution which is the energy integral of the spectrum x-ray source. However, the comparison of the cumulative spectral distribution determined with and without the lens by micro-XRF can be employed to characterize its focalization lens. In this work the development of an analytical approach employing this idea is presented and applied to characterize the focalization lens of our laboratory. After that a standardless calibration of the micro-XRF spectrometer by FP was developed and validated by quantication of reference standards.