The Neoclassical toroidal viscosity caused by perturbed bounce harmonic resonance

Matsuoka, Seikichi ; Idomura, Yasuhiro   ; Satake, Shinsuke*

Effects of non-axisymmetric magnetic field perturbations in tokamaks have attracted much attention from the view point of the control of the plasma performance and instabilities. Recent studies pointed out that there exists qualitative discrepancy of the NTV prediction between a theoretical bounce-averaged model and a global kinetic simulation. Clarifying the cause of the discrepancy is a key issue to establish a reliable basis for the NTV predictions. In this work, we perform two types of global kinetic simulations for the NTV to investigate the discrepancy from the theoretical model. As a result, it is first demonstrated that the discrepancy arises owing to the following two mechanisms; (1) resonant structures predicted in the bounce-averaged model become weak due to global particle orbit width effects, and (2) the velocity space structures are damped by the phase mixing.