The development of quantitative X-ray microanalysis in the 1950s spurred the need for knowledge of the many parameters which describe the electron interaction, such as the ionization cross-sections, fluorescent yields, the electron stopping power, mass absorption coefficients, and others. Although classical microanalysis, which proceeds by measurements of the unknown specimen against a standard, can eliminate the need to know many of these parameters accurately, much current microanalysis is done on highly inhomogeneous samples for which comparison with a standard is much less useful procedure. The increased use of low beam energies also means that data is now required for L-, and M-lines which previously have been little used. Consequently there is an enhanced need for a reliable and agreed set of data on which to base calculations.

A common misconception is the belief that all of the quantities that are needed must already have been measured by somebody and so it is simply a matter of accessing this data.