Quantitative XRFA of carbon in a special matrix by the fundamental parameter method

Abstract

We report on results obtained from experiments using specially prepared carbon substrates and treatment of the data by means of recently introduced theory. Medium Z grids with known parameters have been coated on top of pyrolytic carbon substrates to achieve well defined absorption geometries. The various copper grids exhibit satisfactory performance in terms of mechanical stability, homogeneity and uniformity of the coating. A detailed study of the measurement results shows that there is a more rapid increase of the associated C-K{alpha} countrate from the coated samples compared to the pure elements and is attributed to the contribution of secondary enhancement effects, including those resulting from photoelectrons generated after the primary ionization. A variety of multilayer analyzers has also been evaluated during these experiments. Only a certain combination of muitilayer component materials have been found to be appropriate for use as dispersing elements due to the reflectivity and spatial resolution requirements of our long wavelength spectrometer. Another experimental factor is the low intensity of available tube photons which is due to the selection of the target material and absorption effects in the target as well as the tube window. 12 refs., 7 figs., 2 tabs.