Characterization of low frequency inter-ELM modes at the pedestal top of H-mode discharges at ASDEX Upgrade

Edge Physics Forum

  • Date: Apr 18, 2018
  • Time: 03:30 PM - 04:30 PM (Local Time Germany)
  • Speaker: Branka Vanovac
  • DIFFER - Dutch Institute for Fundamental Energy Research
  • Location: Garching
  • Room: Seminarraum D3
Information from a single diagnostic system is not necessarily sufficient to determine the structure of the mode. This is especially true when diagnosing such a narrow region as the plasma pedestal characterized by steep gradients. In this work, several diagnostics are used to allow for a high degree of characterization of the low frequency modes appearing in between type-I Edge Localizes Modes (ELMs) at the pedestal top of the ASDEX Upgrade plasmas. These modes are measured as temperature (Te) and density (ne) fluctuations, and occasionally as fluctuations in the radial magnetic field (Br). Measured mode velocities are found to be in agreement with the background plasma flow at the position of the modes. The frequency of the mode changes for different heating power levels, which is mainly driven by the change in toroidal rotation. The poloidal structure of the modes is resolved with the Electron Cyclotron Emission Imaging (ECEI) measurements. Bicoherence of the magnetic signal between different frequency branches is evaluated and discussed. It is addressed whether the modes could be resistive in nature.
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