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Idomura, Yasuhiro
Physics of Plasmas, 24(8), p.080701_1 - 080701_5, 2017/08
Times Cited Count：10 Percentile：45.63(Physics, Fluids & Plasmas)An electron heating modulation numerical experiment based on a global full-f gyrokinetic model shows that transitions from ion temperature gradient driven (ITG) turbulence to trapped electron mode (TEM) turbulence induced by electron heating generate density peaking and rotation changes. Toroidal angular momentum balance during the rotation changes is revealed by direct observation of toroidal angular momentum conservation, in which in addition to ion turbulent stress, ion neoclassical stress, radial currents, and toroidal field stress of ions and electrons are important. Toroidal torque flipping between ITG and TEM phases is found to be related to reversal of the ion radial current that indicates coupling of particle and momentum transport channels. The ion and electron radial currents are balanced to satisfy the ambipolar condition, and the electron radial current is cancelled by the electron toroidal field stress, which indirectly affects toroidal torque.
*; Miura, Yukitoshi; Matsuda, Toshiaki; Ito, Kimitaka; JFT-2M Group
NIFS-241, 16 Pages, 1993/08
no abstracts in English
Hirayama, Toshio; Kikuchi, Mitsuru; Shirai, Hiroshi; Shimizu, Katsuhiro; Yagi, Masatoshi; Koide, Yoshihiko
Kaku Yugo Kenkyu, 65(SPECIAL ISSUE), p.75 - 97, 1991/03
no abstracts in English
Idomura, Yasuhiro
no journal, ,
Comparisons between flux driven full-f gyrokinetic simulations and gradient driven delta-f gyrokinetic simulations are discussed with respect to i) turbulent momentum transport and ii) plasma size and power scaling of ion temperature gradient driven turbulence. In the former problem, the ambipolar condition including both turbulent and neoclassical transport is essential in estimating momentum transport and resulting plasma rotation profiles. In the latter problem, self-consistent interactions between temperature fluctuations and turbulent transport under a local power balance condition lead to the power degradation of confinement. These mechanisms are unique to full-f simulations and give significant impact on the estimation of plasma confinement performances.
Idomura, Yasuhiro
no journal, ,
In this talk, we review theoretical understanding on momentum transport in full-f gyrokinetic simulations. Firstly, we discuss the validity of the present theoretical framework based on the first order gyrokinetics by showing the toroidal angular momentum conservation. Secondly, a relation between non-diffusive momentum transport and up-down asymmetry of turbulent mode structures is shown based on the profile shear induced residual stress theory. Finally, a mechanism to sustain intrinsic rotation profiles in steady plasmas is discussed based on the toroidal angular momentum conservation.
Idomura, Yasuhiro
no journal, ,
Reversal or change of plasma rotation is one of outstanding issues in recent momentum transport tokamak experiments. We address this issue based on numerical experiments using a Gyrokinetic Toroidal 5D full-f Eulerian code GT5D, in which detailed mechanisms of momentum transport and the resulting plasma rotation can be analysed from direct observation of the toroidal angular momentum conservation. In many tokamaks, rotation changes are commonly observed by applying electron cyclotron resonance heating without momentum input. The rotation changes induced by electron heating is reproduced for the first time by the numerical experiment, and it is found that a change of turbulent momentum transport between ion turbulence to electron turbulence plays a critical role.
Idomura, Yasuhiro
no journal, ,
A Gyrokinetic Toroidal 5D full-f Eulerian code GT5D is extended including a new hybrid kinetic electron model, which enables us to address ITER relevant issues related to electron turbulence. In this talk, physics backgrounds and computational properties of the new hybrid kinetic electron model are discussed, and applications of the model to ITER relevant issues such as the isotope effect of turbulent plasma transport and the plasma rotation change induced by electron heating are presented. These simulation studies show that electron turbulence plays a critical role in ITER, and thus, the new hybrid kinetic electron model is essential for analyzing the performance of core plasmas in ITER.
Idomura, Yasuhiro
no journal, ,
Turbulent momentum transport, which is considered to dictate plasma rotation in ITER, is one of critical issues in the International Tokamak Physics Activity. In particular, in recent years, plasma rotation changes induced by electron cyclotron heating, which does not have momentum input, have attracted attention as a phenomenon, which indicates transition of turbulent momentum transport. However, its physical mechanism has been open. In this work, we successfully reproduced this phenomena in numerical experiments using a Gyrokinetic Toroidal 5D full-f Eulerian code GT5D. Based on a direct observation of the toroidal angular momentum conservation, it is found that turbulent momentum transport is changed by a transition of dominant turbulence from ion turbulence to electron turbulence induced by electron heating.
