Berlin 2024 – scientific programme
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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 9: KFM Poster Session
KFM 9.19: Poster
Monday, March 18, 2024, 18:00–20:00, Poster E
Leveraging Automatic Differentiation in Complex Model Fitting — •Erik Thiessenhusen1, Ritz Aguilar1, Michal Smid1, Thomas Kluge1, Michael Bussmann1, 2, Thomas Cowan1, Nico Hoffmann1, Lingen Huang1, and Jeffrey Kelling1 — 1Helmholtz-Zentrum Dresden-Rossendorf — 2Center for Advanced Sytem Understanding
Understanding laser-solid interactions is important for the development of laser-driven particle and photon sources, e.g., tumor therapy, astrophysics, and fusion. Currently, these interactions can only be modeled by simulations that need to be verified experimentally. Consequently, pump-probe experiments were conducted to examine the laser-plasma interaction that occurs when a high intensity laser hits a solid target. Since we aim for a femtosecond temporal and nanometer spatial resolution at European XFEL, we employ Small-Angle X-ray Scattering (SAXS) and Phase Contrast Imaging (PCI) that can each be approximated by an analytical propagator. In our reconstruction of the target, we employ a gradient descent algorithm that iteratively minimizes the error between experimental and synthetic patterns propagated from proposed target structures. By implementing the propagator in PyTorch we leverage the automatic differentiation capabilities, as well as the speed-up by computing the process on a GPU. We perform a scan of different initial parameters to find the global minimum, which is accelerated by batching multiple parallel reconstructions.
Keywords: SAXS; PyTorch; X-Ray; Phase Retrieval