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Maeyama, Shinya; Watanabe, Tomohiko*; Idomura, Yasuhiro; Nakata, Motoki; Yagi, Masatoshi; Miyato, Naoaki; Nunami, Masanori*; Ishizawa, Akihiro*
no journal, ,
no abstracts in English
Idomura, Yasuhiro
no journal, ,
Progress of confinement studies on ion temperature gradient driven (ITG) turbulence using the gyrokinetic full-f Eulerian code GT5D is reviewed. GT5D enabled long time turbulence calculations with fixed heating power, where turbulent transport and plasma profiles are determined in a consistent manner. In heating power scan of the ITG turbulence, the power degradation of confinement, which is universally observed in tokamak experiments, is recovered. The plasma size scaling of the confinement is studied using ITER-size numerical experiments, and it is found that confinement properties of large devices are affected by the heating power scaling. Relations between the plasma size scaling and differences of confinement properties between hydrogen and deuterium plasmas are clarified.
Miyato, Naoaki
no journal, ,
Since the standard gyrokinetic model is formulated through the two-step phase space transformation, it is possible to represent fluid moments in terms of gyro-center things in two ways. The two representations are compared in the electrostatic limit. It is shown that some difference appears in deriving particle flux representation including finite Larmor radius effects. When we use the representation used in the standard formulation, higher-order solution is needed for the generating function of the gyro-center transformation. On the other hand, only the lowest solution is sufficient for the alternative representation.
Miki, Kazuhiro; Idomura, Yasuhiro
no journal, ,
Energetic particles physics is of importance in the community of transport and confinement towards the future burning plasmas. We here introduce energetic particles in a full-f gyrokinetic code (GT5D). We find linear dynamics of the EGAM driven by bump-on-tail particle distributions. We examine flat-q, homogeneous, axisymmetric, electrostatic gyrokinetic simulations. Above a certain level of the beam intensity, an oscillatory mode grows with about a half of the standard GAM. The observed frequencies are consistent with the eigenmode analyses derived from the perturbed gyrokinetic equations. The theoretical analyses also indicate a bifurcation of the excited modes depending on q-value. Estimation of the finite-orbit-width effects can provide a size dependency of the EGAM growth rate. We find linear and nonlinear dynamics of the EGAM driven by slowing-down distributions. We examine the axisymmetric gyrokinetic simulations with DIII-D-like parameters. The observed growth rates and frequencies are consistent with results of other hybrid code.
Matsuoka, Seikichi; Idomura, Yasuhiro; Satake, Shinsuke*
no journal, ,
Effects of non-axisymmetric magnetic field perturbations have attracted much attention from the view point of the control of the plasma performance and instabilities. The perturbations cause the neoclassical toroidal viscosity (NTV) due to the non-ambipolar particle transport. Recent studies pointed out that the qualitative discrepancy of the NTV prediction exist between a theoretical bounce-averaged model and a global kinetic simulation. It is crucial to clarify the cause of the discrepancy 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 due to the following two mechanisms; the absence of the magnetic field shear effect in the bounce-averaged model and the so-called transient particle orbit caused by the non-axisymmetric perturbations.