X-ray fluorescence spectrum excitation theory is now well developed and uses the assumption that the primary X-ray radiation beam is parallel. At the same time, in order to increase intensity it is necessary to keep the radiation source and fluorescence object as close as possible. In so doing the primary radiation divergence is found to be significant, and to ensure high accuracy of the intensity calculations it is necessary to evaluate the influence of this factor.Considerations are carried out for the cases of point, circular and line sources of primary radiation, selective effects being absent.The concept of the effective incidence angle is introduced which makes it possible to calculate X-ray fluorescence intensities by formulae without correction for the primary radiation divergence. Values of the correction coefficients are given which correct for the dependence of the effective angle on chemical composition of the fluorescence material. The value of the effective incidence angle of primary radiation for a circular source is determined and compared with its theoretical value. Statistical treatment of the results shows insignificant differences between the experimental intensities and those calculated with correction for the primary radiation divergence when chemical composition variation of the material analysed is quite large.Px sin @ deo = ____ dx d a 4n(hZ t X*) Introducing Eqn (1) into the formula for X-ray fluorescence intensity suggested in Ref. 2, we obtain the following expression for the radiation energy of element A emitted by the elemental dS section:where CAconcentration of element A hAfluorescence radiation wavelength of element A p(X), @(AA) -mass absorption coefficient of the sample for the primary radiation of wavelength h and for the fluorescence radiation of wavelength hA /.LA&), rA(hA) -attenuation coefficient and true absorption coefficient, respectively, of element A for the radiation wavelength XA S,", ok,P& -absorption jump, fluorescence yield of level K and probability of transition emitting line i of K series of element A respectively $J -incidence angle of the primary radiation on the sample J/ -emergence angle of the fluorescence radiation
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