19th IAEA Fusion Energy Conference

Gyrokinetic Global Analysis of Ion Temperature Gradient Driven Mode in Reversed Shear Tokamaks

Y. Idomura, S. Tokuda, Y. Kishimoto
Department of Fusion Plasma Research, Naka Fusion Research Establishment, Japan Atomic Energy Research Institute, Naka, Ibaraki, 311-0193, Japan

Abstract.
A new toroidal gyrokinetic particle code has been developed to study the ion temperature gradient driven (ITG) turbulence in reactor relevant tokamak parameters. We use a new method based on a canonical Maxwellian distribution F_CM (P_φ,ε, μ), which is defined by three constants of motion in the axisymmetric toroidal system, the canonical angular momentum P_φ, the energy ε, and the magnetic moment μ. A quasi-ballooning representation enables linear and nonlinear high-m,n global calculations with a good numerical convergence. Conservation properties are improved by using the optimized loading method [2]. From comprehensive linear global analyses over a wide range of an unstable toroidal mode number spectrum (n=0~100) in large tokamak parameters (a/ρ_ti=320~460), properties of the ITG modes in reversed shear tokamaks are discussed. In the nonlinear simulation, it is found that a new method based on F_CM can simulate a zonal flow damping correctly, and spurious zonal flow oscillations, which are observed in a conventional method based on a local Maxwellian distribution F_LM(ψ, ε, μ), do not appear in the nonlinear regime.