Many variables influence the performance of X-ray fluorescence analysis with regard to speed, precision, accuracy, limits of detection and the elements to be determined. Some of these variables, such as path transmittance, fluorescent yield, and detector efficiency, can be considered constant; however, the primary X-ray beam cannot be assumed a constant. The intensity distribution vs. wavelength function of the X-ray tube remains the main variable with which the X-ray spectrochemist must concern himself in providing optimum analytical performance and speed.

This distribution is dependent upon target material, window material and thickness, and tube voltage. Though the overall intensity is dependent upon the atomic number of the target material, the wavelengths of the characteristic line spectrum of the target material can provide additional enhancement for elements which absorb such wavelengths readily.

Some of these variables in tube design parameters have been studied to provide comparison performance data on the analysis of a variety of base materials for a number of elements of interest. These data and their interpretation are presented to show how improved fluorescence analysis can be achieved by modifications in X-ray tube design and manufacture.