Regensburg 2022 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 3: Microscopy and Tomography with X-ray, Photons, Electrons, Ions and Positrons

KFM 3.2: Vortrag

Montag, 5. September 2022, 09:50–10:10, H7

Flat-field correction of highly-dynamic processes — •Thea Engler1, Johannes Hagemann1, Christian Schroer1, and Mathias Trabs21Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany — 2Karlsruhe Institue of Technology KIT, Germany

Using hard coherent x-rays, as produced in PETRA III at DESY and in the European XFEL, objects with a size of μm to nm can be imaged with full-field phase-contrast imaging. With single-pulse imaging, specifically dynamic processes on the nanosecond-timescales can be investigated. A recorded single-pulse hologram of the object under investigation in a lens-less imaging setup is disturbed by illumination artifacts. The origin of these artifacts are aberrations in the optics, such as figure errors and surface roughness. For further analysis, the illumination artifacts have to be removed, which is achieved by a flat-field correction. Therefore, the x-ray image of the object of interest is divided by an empty-beam image. This approach assumes temporal stability of both illumination and object. In the case of XFEL experiments, the pulse-to-pulse fluctuations stemming from the SASE process violate this assumption. For the imaging conducted at PETRA III, in addition to vibrations in the beamline's optical components, the object itself incorporates dynamic movements. The common case of the flat-field correction can be improved by recording an empty-beam image-series. With principal component analysis (PCA) of the image series and a careful selection of the principal components, a synthetic flat-field can be reconstructed for each object-image.

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