Berlin 2014 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 67: Photonics III

Q 67.8: Talk

Friday, March 21, 2014, 18:15–18:30, UDL HS3038

Ptychography in Energy-Time Space for Mössbauer Spectroscopy — •Johann Haber and Ralf Röhlsberger — Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg

Ptychography is a phase retrieval method that has recently been the subject of much attention in the fields of x-ray microscopy and phase contrast imaging. The x-ray beam, called probe, scans a sample, called object, in discrete steps. At every position the diffraction pattern is recorded. The measured amplitudes and the knowledge of the position of the probe at the time of their measurement form the so-called amplitude and probe constraints. An iterative phase retrieval algorithm is then able to reconstruct from random initial guesses the object and probe amplitudes and phases. Here, we extend this principle to phase retrieval of signals in energy and temporal domains. The object is the response function of a sample containing ⁵⁷Fe. The response function of the sample is scanned in energy space by an analyzer foil. For each energy step, a temporal beat pattern is measured. This gives us amplitude constraints in both energy and temporal space and a probe constraint to apply in the algorithm, which should enhance its stability. We apply the algorithm to simulations and measurements and discuss its sensitivity to noise and incomplete sampling in the temporal domain.