Exploring Turbulence in Fusion Plasmas through Experiment and Simulation

Institutskolloquium

  • Date: Oct 12, 2018
  • Time: 10:30 AM - 12:00 PM (Local Time Germany)
  • Speaker: Dr. Tim Happel
  • IPP
  • Room: Hörsaal D2 (Übertragung nach HGW S1)
A profound understanding of turbulence in fusion plasmas is paramount because of its strong impact on both core and edge plasma transport. Turbulence is a key player in determining particle, energy, and momentum fluxes and thus dictates the shape of the density, temperature, and rotation profiles, which set the the efficiency of a fusion reactor. Gyrokinetic theory is considered nowadays to be the state of the art when it comes to a compromise between realism and efficiency, but must be validated to improve the reliability of predicting profiles for future fusion devices. The fundamentals of turbulence, its generation and its characterization with both measurements and simulations will be presented. For the core plasma, particular attention is paid to the comparison between measurements and gyrokinetic simulations, which has led to significant gains in understanding. The edge turbulence behavior in different confinement regimes is contrasted. Strong turbulence is usually observed in the L-mode edge while the H-mode edge plasma exhibits a reduced turbulence level. In yet another confinement regime, the improved energy confinement mode (I-mode), edge turbulence is reduced to a large degree. However, strongly intermittent high amplitude events are observed. An analytic candidate generation mechanisms is presented and first results from accompanying gyrokinetic simulations of the I-mode edge – consistent with the observations – are reported.
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