Effect of Triangularity on Ion-Temperature-Gradient-Driven Turbulence

POSTER

Abstract

Transport driven by ion temperature gradient (ITG) turbulence is an important loss channel in tokamaks. We model how changing triangularity δ, both negative and positive, affects ITG linear growth rates and turbulent saturation. Linear and nonlinear properties of an ITG scenario with adiabatic electrons are analyzed using the gyrokinetic code GENE. Peak linear growth rates decrease with negative δ but increase in finite radial wavenumber kx with positive δ. The growth-rate spectrum broadens in kx with negative δ and significantly narrows with positive δ. The effect of δ on linear instability properties can be explained through its impact on field line bending and curvature. Nonlinear heat flux is weakly dependent on triangularity for |δ| ≤ 0.5, decreasing significantly with extreme δ, regardless of sign. Zonal modes play an important role in nonlinear saturation in the configurations studied, and artificially suppressing zonal modes increased nonlinear heat flux by a factor of about four for negative δ, increasing with positive δ to almost a factor of 20. Proxies for zonal-flow damping and drive suggest that zonal flows are enhanced with increasing positive δ.

*This work is supported by the US Department of Energy, Office of Science, Fusion Energy Services under grants nos. DE-FG02-86ER53218, DE-FG02-99ER54546, DE-FG02-93ER54222, DE-FG02-89ER53291, DE-FG02-93ER54222, and DE-AR0001287 and by the EUROfusion -- Theory and Advanced Simulation Coordination (E-TASC). This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training program 2014-2018 and 2019-2020 under grant agreement no. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. Computing resources were provided through the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility, grant no. DE-AC02-05CH11231.

Publication: J. M. Duff, B. J. Faber, C. C. Hegna, M. J. Pueschel, and P.W. Terry, "Effect of Triangularity on Ion-Temperature-Gradient-Driven Turbulence", Phys. Plasmas, to be submitted shortly

Presenters

  • Joey M Duff

    • University of Wisconsin-Madison
    • University of Wisconsin - Madison

Authors

  • Joey M Duff

    • University of Wisconsin-Madison
    • University of Wisconsin - Madison

  • Benjamin Faber

    • University of Wisconsin - Madison
    • UW Madison

  • Chris C Hegna

    • University of Wisconsin - Madison

  • M.J. Pueschel

    • Dutch Institute for Fundamental Energy Research
    • Dutch Institue for Fundamental Energy Research, Eindhoven, The Netherlands; Eindhoven University of Technology, Eindhoven, The Netherlands

  • Paul W Terry

    • University of Wisconsin - Madison