SMuK 2021 – scientific programme
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P: Fachverband Plasmaphysik
P 5: Poster I
P 5.36: Poster
Tuesday, August 31, 2021, 14:00–16:00, P
Fast characterization of plasma states in W7-X with permutation entropy — •Juan Fernando Guerrero Arnaiz1,2, Andreas Dinklage1,2, Bernd Pompe1, Matthias Hirsch2, Udo Höfel2, Christian Brandt2, Henning Thomsen2, Jonathan Schilling2, Kian Rahbarnia2, Tamara Andreeva2, Ulrich Neuner2, and the W7-X Team2 — 1Universität Greifswald, Greifswald Germany — 2Max-Planck-Institut für Plasmaphysik, Greifswald Germany
Permutation entropy (PE) is applied on time series of plasma measurements. PE is a single number that represents the information rate to derive the ordinal properties of a time series. Here, we systematically characterize, by means of the PE, highly sampled multi-variate signals from a 32-channel electron cyclotron emission radiometer. Being capable to detect changes in bulk data, core localized spatio-temporal bifurcations of the plasma states were revealed from changes of the PE. Hereby, spontaneous transitions to high core-electron temperatures (Te) were detected at different heating powers and densities in the so-called low-iota configuration of W7-X. The transitions have been seen to go along with the occurrence of low frequency MHD activity, which ceases when Te increases. It is this MHD activity which PE is sensitive to. While visual a-posteriori inspection of the (noisy) data results in similar findings, the time to identify changes is much reduced. Therefore, PE is suggested to be employed for machine learning techniques to identify plasma state changes.