Calculation of x-ray tube spectral distributions

Abstract

Two approaches to the calculation of x-ray tube spectral distributions for x-ray fluorescence analysis are compared. One of them is the NIST algorithm based both on Kramers' law for the continuum intensity and a semi-empirical ratio between the characteristic lines and the continuum intensity. In the other, the continuum and characteristic spectra are calculated separately just as it is done in electron microprobe analysis. Some improvements concerned with the description of the shape of the continuum spectrum at long wavelength and correction for fluorescence excited by the bremsstrahlung spectrum are proposed. The calculations of the continuum intensity and the relationship between the integral continuum and the characteristic line intensities were compared with literature experimental data for Cr, Rh, W, Cu and Mo target tubes. Some estimations of the absolute intensities of x-ray tube spectra are also shown. Copyright © 1999 John Wiley & Sons, Ltd.