Erlangen 2018 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 22: Atomic Clusters II (joint session A/MO)
A 22.6: Vortrag
Dienstag, 6. März 2018, 15:15–15:30, K 2.016
Holography combined with iterative phase retrieval: advances in coherent diffractive imaging of single nanoparticles — •Felix Zimmermann1, Tais Gorkhover2, Daniela Rupp1,3, Thomas Möller1, and Anatoli Ulmer1 — 1TU Berlin — 2LCLS@SLAC — 3MBI Berlin
Free-Electron-Lasers open the door to high-resolution images of non-cristallin nanoparticles such as viruses via coherent diffraction of single X-ray pulses. The phase loss problem impedes the extraction of high resolution structural information from the recorded diffraction patterns. Two major approaches address this problem. First, one can recover the phase during post processing using iterative algorithms. Second, one can directly encode the phase into the image using reference scatterers as common in holography. The limitations and advantages of iterative and holographic methods differ significantly: iterative algorithms can reconstruct the sample from its diffraction patterns alone, but require a priori constraints and rely on human input. Usually, a number of independent reconstructions using different starting values have to be performed. The final result is based on the average of these reconstructions. In holography, a unique reconstruction without prior knowledge can be performed via simple calculations based on the Fourier transformation, but the result is degraded by the transfer function given by the reference. This talk will discuss whether a combination of both approaches might be advantageous regarding stability, computational complexity and achievable fidelity.