Observation of Edge Filamentary Structure Motion during Supersonic Molecular-Beam Injection Using a Fast Camera in Heliotron J

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Abstract

A perpendicular-view fast video camera has been installed in Heliotron J to observe the behavior of filamentary structures of edge plasma turbulence across the last closed flux surface (LCFS). Supersonic molecular-beam injection (SMBI) can greatly increase the edge Hα emission; hence, we used the high imaging rate and shutter speed of the camera to capture the behavior of the fast propagating filamentary structures. A high-pass fast Fourier transform filter on the time dimension was adopted to extract the fluctuation component from the raw data for each pixel. The motion of the filamentary structures was clearly visible when we applied an amplitude threshold to identify the intense structures. In addition, a time-resolved 2D cross-correlation technique was adopted to estimate the poloidal phase velocity of turbulence. The motion direction was found to be reversed dramatically just after an SMBI pulse.

Journal

  • Plasma and Fusion Research

    Plasma and Fusion Research 8(0), 1402066-1402066, 2013

    The Japan Society of Plasma Science and Nuclear Fusion Research

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