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Average a(EX)-values of elements and oxides and percentage differences calculated using the XCOM and FFAST attenuation coefficients; uncertainties, seen in italics, apply to the rightmost decimal place of the data Abstract Proton-induced x-ray emission (PIXE) was used to assess the accuracy of the National Institute of Standards and Technology XCOM and FFAST photo-ionization cross-section databases in the low energy region (1–2 keV) for light elements

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posted on 2013-09-06, 00:00 authored by C M Heirwegh, I Pradler, J L Campbell

Table 3. Average a(EX)-values of elements and oxides and percentage differences calculated using the XCOM and FFAST attenuation coefficients; uncertainties, seen in italics, apply to the rightmost decimal place of the data

Abstract

Proton-induced x-ray emission (PIXE) was used to assess the accuracy of the National Institute of Standards and Technology XCOM and FFAST photo-ionization cross-section databases in the low energy region (1–2 keV) for light elements. Characteristic x-ray yields generated in thick samples of Mg, Al and Si in elemental and oxide form, were compared to fundamental parameters computations of the expected x-ray yields; the database for this computation included XCOM attenuation coefficients. The resultant PIXE instrumental efficiency constant was found to differ by 4–6% between each element and its oxide. This discrepancy was traced to use of the XCOM Hartree–Slater photo-electric cross-sections. Substitution of the FFAST Hartree–Slater cross-sections reduced the effect. This suggests that for 1–2 keV x-rays in light element absorbers, the FFAST predictions of the photo-electric cross-sections are more accurate than the XCOM values.

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