Berlin 2018 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 33: Poster Session III

CPP 33.15: Poster

Dienstag, 13. März 2018, 14:00–16:00, Poster C

A new approach to evaluate the phase gradient in diffusion measurements by digital interferometry — •Daniel Sommermann, Thomas Triller, and Werner Köhler — Institute of Physics, University of Bayreuth, 95440 Bayreuth, Germany

In order to get a better understanding of thermodiffusion in ternary mixtures, the so called DCMIX experiments (Diffusion Coefficients in MIXtures) were performed on the International Space Station (ISS) using the SODI-interferometer (Selective Optical Diagnostics Instrument) under microgravity conditions. This Mach-Zehnder-Interferometer measures the Soret effect by applying a vertical temperature gradient to the system and using digital interferometry with laser phase stepping for readout.

Information about mass diffusion coefficients is obtained by an evaluation of the phase of the interferogram which is done by temporal phase shifting using five pictures in a row. Unfortunately, the readout laser in the DCMIX3 microgravity experiments suffered from instabilities and phase fluctuations. Usual temporal phase shifting algorithms are expecting a constant change in phase and are therefore unable to evaluate part of the data.

In this work a new spatial evaluation methode is introduced which can handle the problem of nonconstant phase stepping by analysing all pictures individually, thereby reconstructing the phase gradient.