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(TH/P1-08) Gyrokinetic Global Analysis of Ion Temperature Gradient Driven Mode in Reversed Shear Tokamaks

Y. Idomura¹⁾, S. Tokuda¹⁾, Y. Kishimoto^1)
 
1) Japan Atomic Energy Research Institute, Ibaraki, Japan

Abstract.  The ion temperature gradient driven (ITG) mode in reactor relevant large tokamak parameters ( a/$\rho_{i}^{}$ = 320 - 460) is studied using a newly developed gyrokinetic toroidal particle code. From comprehensive global analyses over a wide range of an unstable toroidal mode number spectrum (n=0-100), it is found that especially in reversed shear tokamaks, properties of the ITG mode are drastically changed through ion heating and density peaking processes. If the ion temperature is sufficiently high, high-n modes, which are much more unstable than low-n modes, are excluded from the q_min region of reversed shear tokamaks, because of a geometry effect 1/r and the finite Larmor radius effect in an unstable condition in a wave number space k_$\theta$$\rho_{i}$ = nq(r)/r$\rho_{i}$ = 0.5. On the other hand, these global effects become weak in normal shear tokamaks, because the effects are compensated by monotonically increasing q(r). Residual low-n global modes in the q_min region show slab like feature, and their growth rates decrease by a peaked density profile.

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