Directional dark-field implicit x-ray speckle tracking using an anisotropic-diffusion Fokker-Planck equation - Archive ouverte HAL
Article Dans Une Revue Physical Review A Année : 2021

Directional dark-field implicit x-ray speckle tracking using an anisotropic-diffusion Fokker-Planck equation

Résumé

When a macroscopic-sized noncrystalline sample is illuminated using coherent x-ray radiation, a bifurcation of photon energy flow may occur. The coarse-grained complex refractive index of the sample may be considered to attenuate and refract the incident coherent beam, leading to a coherent component of the transmitted beam. Spatially unresolved sample microstructure, associated with the fine-grained components of the complex refractive index, introduces a diffuse component to the transmitted beam. This diffuse photon-scattering channel may be viewed in terms of position-dependent fans of ultrasmall-angle x-ray scatter. These position-dependent fans, at the exit surface of the object, may under certain circumstances be approximated as having a locally elliptical shape. By using an anisotropic-diffusion Fokker-Planck approach to model this bifurcated x-ray energy flow, we show how all three components (attenuation, refraction, and locally elliptical diffuse scatter) may be recovered. This is done via x-ray speckle tracking, in which the sample is illuminated with spatially random x-ray fields generated by coherent illumination of a spatially random membrane. The theory is developed and then successfully applied to experimental x-ray data.

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Dates et versions

hal-03600506 , version 1 (14-10-2024)

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Konstantin Pavlov, David Paganin, Kaye Morgan, Heyang (thomas) Li, Sebastien Berujon, et al.. Directional dark-field implicit x-ray speckle tracking using an anisotropic-diffusion Fokker-Planck equation. Physical Review A, 2021, 104 (5), pp.053505. ⟨10.1103/PhysRevA.104.053505⟩. ⟨hal-03600506⟩
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