Novel 2D velocity estimation method for large transient events in plasmas

Lampert, Mate ; Diallo, Ahmed ; Zweben, Stewart
Issue date: 2021
Rights:
Creative Commons Attribution 4.0 International (CC BY)
Cite as:
Lampert, Mate, Diallo, Ahmed, & Zweben, Stewart. (2021). Novel 2D velocity estimation method for large transient events in plasmas [Data set]. Princeton Plasma Physics Laboratory, Princeton University. https://doi.org/10.11578/1814959
@electronic{lampert_mate_2021,
  author      = {Lampert, Mate and
                Diallo, Ahmed and
                Zweben, Stewart},
  title       = {{Novel 2D velocity estimation method for
                large transient events in plasmas}},
  publisher   = {{Princeton Plasma Physics Laboratory, Pri
                nceton University}},
  year        = 2021,
  url         = {https://doi.org/10.11578/1814959}
}
Description:

Dynamics of fast transient events are challenging to be analyzed with high time resolution. Such events can occur in fusion plasmas such as the filaments during edge-localized modes (ELMs). In this paper, we present a robust method—the spatial displacement estimation—for estimating the displacements of structures with fast dynamics from high spatial and time resolution imaging diagnostics [e.g., gas-puff imaging (GPI)] with sampling time temporal resolution. First, a background suppression method is shown, which suppresses the slowly time-evolving and spatially non-uniform background in the signal. In the second step, a two-dimensional polynomial trend subtraction method is presented to tackle the remaining polynomial order trend in the signal. After performing these pre-processing steps, the spatial displacement of the propagating structure is estimated from the two-dimensional spatial cross-correlation coefficient function calculated between consecutive frames. The method is tested for its robustness and accuracy by simulated Gaussian events and spatially displaced random noise. An example application of the method is presented on propagating ELM filaments measured by the GPI system on the National Spherical Torus Experiment spherical tokamak.

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