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Proceedings Paper

Effective density and atomic number determined from diffraction profiles
Author(s): Geoffrey Harding
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Paper Abstract

X-ray diffraction (XRD) profiles are conventionally used to determine lattice spacings via Bragg's law in order to characterize crystalline materials. It does not appear to be widely known that they also permit compositional information, such as effective atomic number and a density descriptor, to be determined from materials having little or no crystal structure. A ratio method is introduced that relates x-ray scatter intensities in two adjacent momentum transfer bands of the diffraction profile corresponding to the "tip" region of the primary x-ray spectrum. It is shown that this ratio depends on the effective atomic number, Z, of the scattering sample. Conversely, Z may be derived from measurement of the ratio. Error sources in this ratio method are briefly analyzed. Once Z is known, the IAM (independent atom model) cross section can be extrapolated from the high momentum transfer region to lower values, where molecular interference effects manifest themselves in the XRD profile. This procedure enables the molecular interference function, s(x), to be determined. On the assumption that the structure of liquids and amorphous materials can be represented by the hard sphere (HS) model, the packing fraction, η, of atoms in the scattering sample can be ascertained from the second moment of s(x). The effective atomic number, Z and the density descriptor, η, usefully complement information provided by more traditional material analysis techniques based on XRD profiles.

Paper Details

Date Published: 21 September 2006
PDF: 9 pages
Proc. SPIE 6319, Hard X-Ray and Gamma-Ray Detector Physics and Penetrating Radiation Systems VIII, 63191O (21 September 2006); doi: 10.1117/12.687620
Show Author Affiliations
Geoffrey Harding, GE Security Germany (Germany)


Published in SPIE Proceedings Vol. 6319:
Hard X-Ray and Gamma-Ray Detector Physics and Penetrating Radiation Systems VIII
F. Patrick Doty; Larry A. Franks; Arnold Burger; H. Bradford Barber; Hans Roehrig; Ralph B. James, Editor(s)

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