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Proceedings Paper

Measured 1 to 40 keV Photoabsorption Cross Sections for: Fe, Ni, Sn, Ta, Pt, Au, Pb, U
Author(s): Nancy Kerr Del Grande
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Paper Abstract

Total absolute photoabsorption cross sections were measured at 1 keV to 40 keV for Fe, Ni, Sn, Ta, Pt, Au, Pb and U. Overall measurement uncertainties were 3%, less than 2% of which were statistical. The measurements tested widely-used theoretical and experimental tables. They favored relativistic Hartree-Slater atomic calculations. Agreement with theory was typically 5% or better, except near the absorption edge energy region with EXAFS peaks. The measured peak and valley magnitudes for the solid samples ranged from 0% to 20% (with an average of 10%) above the atomic calculations for Fe and Ni. Discrepancies with experimental tables, at energies below 6 keV, were 10% to 40%. Authors of widely-used tables have been fraught with problems where there were few or no prior measurements, only interpolations and,theory. The present measurements used samples from a few hundred to a few thousand μg/cm2, such that the mean free path thicknesses, ppx, were 1 and 3 at 1.5 keV. Samples were vapor-deposited 440, and floated off of, optically flat glass slides. Their weights per unit area, μx g/cm4, were determined within 2% or 3%. Thicker samples, of known weights per unit area, were used for the higher energy measurements. The ratio of ppx for thick and thin samples tested px for the thin samples. Back-scattered protons and alpha particles, as well as ion microanalyses, were used to test the samples' purity. Uranium deposits were sandwiched between two beryllium layers to impede surface oxidation. The transmission measurements were taken with a demountable x-ray tube, vacuum crystal monochromator and flow proportional counter, using slits that provided a narrow-beam geometry.

Paper Details

Date Published: 12 August 1986
PDF: 9 pages
Proc. SPIE 0691, X-Ray Imaging II, (12 August 1986); doi: 10.1117/12.936614
Show Author Affiliations
Nancy Kerr Del Grande, University of California (United States)

Published in SPIE Proceedings Vol. 0691:
X-Ray Imaging II
D. Keith Bowen; Larry V. Knight, Editor(s)

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