Secondary fluorescence correction formulae for X-ray microanalysis — II Self-supporting discs

Geometric factors are derived for correction of secondary fluorescence from self-supporting thinned discs. Fluorescence is considered both when the entire 3 mm disc is exposed to the X-ray detector and when the majority of the specimen is masked by an X-ray opaque washer with a small circular aperture. Geometric factors can be expressed as a ratio of the lengths that characterize fluorescence from these discs. The geometric factors seldom exceed a few percent because self-supporting discs subtend small fractional solid angles from the perspective of the thin edge being analyzed. However, elements composing the disc are fluoresced with equal efficiency by all primary X-rays of energy higher than the ionization energy of the fluoresced element. Fluorescence of self-supporting discs is therefore qualitatively different from fluorescence of parallel-sided thin foils, wedges, and bulk specimens, for which substantial fluorescence occurs only when the energy of the fluorescing primary X-ray barely exceeds the ionization energy of the fluoresced element.