SECONDARY FLUORESCENCE CORRECTION FORMULAS FOR X-RAY-MICROANALYSIS .2. SELF-SUPPORTING DISCS

Geometric factors are derived for correction of secondary fluorescence from self-supporting thinned discs. Fluorescence is considered both w hen 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 s mall circular aperture. Geometric factors can be expressed as a ratio of the lengths that characterize fluorescence from these discs. The ge ometric factors seldom exceed a few percent because self-supporting di scs subtend small fractional solid angles from the perspective of the thin edge being analyzed. However, elements composing the disc are flu oresced with equal efficiency by all primary X-rays of energy higher t han the ionization energy of the fluoresced element. Fluorescence of s elf-supporting discs is therefore qualitatively different from fluores cence of parallel-sided thin foils, wedges, and bulk specimens, for wh ich substantial fluorescence occurs only when the energy of the fluore scing primary X-ray barely exceeds the ionization energy of the fluore sced element.