Dresden 2020 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 5: Microscopy and Spectroscopy with X-rays, Ions and Positrons (joint session KFM/CPP)

KFM 5.3: Vortrag

Montag, 16. März 2020, 15:40–16:00, TOE 317

Experimental optimization of geometry for propagation based phase contrast X-ray imaging — •Hanna Dierks and Jesper Wallentin — Synchrotron Radiation Research, Lund University, Sweden

Propagation-based phase contrast imaging (PB-PCI) with an X-ray lab source is a powerful technique to study low-absorption samples, e.g. soft tissue or plastics, on the micrometer scale. The choice of the propagation distance and magnification is crucial for the performance, and a trade-off in terms of resolution, contrast and noise is always necessary. Theoretical optimization strategies based on Fresnel propagation have been reported, and here we systematically test these experimentally using a setup with a Cu X-ray tube and a detector with 0.55um effective pixel size. The source-detector distance was between 25 and 40cm and magnification ratios were varied from 1 to 1.3. We verify the key conclusions from the proposed models. The experiments show that the theoretical optimization approach is very sensitive to system parameters such as the X-ray source spot size and detector resolution. Moreover, the energy dependence of the refractive index needs to be taken into account when modelling the polychromatic illumination of an x-ray tube. Finally, the sensitivity of TIE based phase retrieval algorithms on the image noise and contrast are studied.