Benchmark of the local drift-kinetic models for neoclassical transport simulation in helical plasmas

Huang, B.*; Satake, Shinsuke*; Kanno, Ryutaro*; Sugama, Hideo*; Matsuoka, Seikichi

Physics of Plasmas, 24(2), p.022503_1 - 022503_19, 2017/02

https://doi.org/10.1063/1.4975611

The drift kinetic equation describes the collisional (neoclassical) transport in plasmas. Recently, a novel radially-local approximation of the drift kinetic equation, which is called the zero orbit width (ZOW) model, is proposed. In this work, as a numerical verification of the neoclassical transport based on the ZOW model, we perform a series of benchmarks of the neoclassical transport and the parallel flow in three helical magnetic configurations using various types of radially-local approximation models including the ZOW model. We found that the neoclassical transport of the ZOW model can reproduce that based on the other models when the radial electric field and thus the drift is large. Also, it is demonstrated that an unphysical large radial transport, which arises in the neoclassical transport of the other models when the drift is small and compared to the magnetic drift, can be mitigated in the ZOW model.

Electromagnetic gyrokinetic simulation of turbulence in torus plasmas

Ishizawa, Akihiro*; Maeyama, Shinya; Watanabe, Tomohiko*; Sugama, Hideo*; Nakajima, Noriyoshi*

Journal of Plasma Physics, 81(2), p.435810203_1 - 435810203_41, 2015/04

https://doi.org/10.1017/S0022377815000100

Electromagnetic gyrokinetic turbulence in finite-beta helical plasmas

Ishizawa, Akihiro*; Watanabe, Tomohiko*; Sugama, Hideo*; Maeyama, Shinya; Nakajima, Noriyoshi*

Physics of Plasmas, 21(5), p.055905_1 - 055905_10, 2014/05

https://doi.org/10.1063/1.4876960

Turbulent transport due to kinetic ballooning modes in high-beta toroidal plasmas

Ishizawa, Akihiro*; Maeyama, Shinya; Watanabe, Tomohiko*; Sugama, Hideo*; Nakajima, Noriyoshi*

Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 8 Pages, 2012/10

http://www-naweb.iaea.org/napc/physics/FEC/FEC2012/papers/386_THP223.pdf

Benchmark test of drift-kinetic and gyrokinetic codes through neoclassical transport simulations

Satake, Shinsuke*; Idomura, Yasuhiro; Sugama, Hideo*; Watanabe, Tomohiko*

Computer Physics Communications, 181(6), p.1069 - 1076, 2010/06

https://doi.org/10.1016/j.cpc.2010.02.014

Two simulation codes that solve the drift-kinetic or gyrokinetic equation in toroidal plasmas are benchmarked by comparing the simulation results of neoclassical transport. In a tokamak configuration, neoclassical radial heat flux and the force balance relation, which relates the parallel mean flow with radial electric field and temperature gradient, are compared between these two codes, and their results are also compared with the local neoclassical transport theory. It is found that the simulation results of the two codes coincide very well in a wide rage of plasma collisionality parameter and also agree with the theoretical estimations. The time evolution of radial electric field and particle flux, and the radial profile of the geodesic acoustic mode frequency also coincide very well.

Kinetic simulations of turbulent fusion plasmas

Idomura, Yasuhiro; Watanabe, Tomohiko*; Sugama, Hideo*

Comptes Rendus Physique, 7(6), p.650 - 669, 2006/07

https://doi.org/10.1016/j.crhy.2006.06.007

In contrast to neutral fluid turbulence described in three-dimensional (3D) configuration space, collisionless magnetised plasma turbulence has been studied using the gyrokinetic model, which is a reduced kinetic model of a plasma in 5D phase space. Recent advances in computer technology and simulation models enabled a direct numerical simulation of plasma turbulence in a toroidal configuration with experimentally relevant parameters. Such kinetic simulations have been established as an essential tool for studying turbulent transport in a fusion plasma. This overview summarises progress in kinetic simulations of turbulent fusion plasmas focusing on physical and numerical models and physical findings obtained from 5D gyrokinetic simulations.

Report on 43rd APS Meeting

Kubo, Hirotaka; Sugama, Hideo*; Murakami, Masakatsu*; Osawa, Yukiharu*

Purazuma, Kaku Yugo Gakkai-Shi, 77(12), p.1252 - 1253, 2001/12

https://ci.nii.ac.jp/naid/110003827578

no abstracts in English

Nonlinear entropy transfer processes in toroidal ITG/ETG turbulence

Nakata, Motoki; Watanabe, Tomohiko*; Sugama, Hideo*; Idomura, Yasuhiro

no journal, , 

In this study, the nonlinear interactions among turbulent vortices and turbulence-induced meso-scale flows, e.g., zonal flows or streamers have been investigated by means of gyrokinetic simulations. Signifiant differences of nonlinear fluctuation (or entropy) transfer processes, which are relevant to the resultant transport levels in the toroidal ITG and ETG turbulence, have been clarified. In the ITG turbulence, nonlinearly generated zonal flows enhance the entropy transfer among non-zonal modes, i.e., the entropy of non-zonal modes is successively transferred to the other non-zonal modes with smaller scales (but with less contribution to the heat flux). On the other hand, in the ETG turbulence, the role of zonal flows in the entropy transfer to smaller scales is much weaker than that in the ITG case. Then, the entropy transfer processes are confined within the non-zonal modes with larger scales where the higher transport level is sustained.

Neoclassical toroidal viscosity calculation method by a particle code based on a local approximation drift-kinetic model

Satake, Shinsuke*; Sugama, Hideo*; Kanno, Ryutaro*; Matsuoka, Seikichi; Idomura, Yasuhiro; Huang, B.*

no journal, , 

The accurate evaluation of the neoclassical toroidal viscosity (NTV) driven by non-axisymmetric external perturbation and/or error field in a tokamak plasma is an important topic in the fusion research, since it can make an influence on the plasma toroidal rotation. This has been widely done so far by analytically and numerically solving the bounce-averaged drift-kinetic equation based on the so-called local approximation, under which the radial drift the particle is neglected. Recently, we have developed two global kinetic simulations based on and full- models respectively. It has been shown that the so-called Superbanana-Plateau collisionality regime expected in the bounce-averaged theory, in which the NTV is independent of the collisionality, is not observed in both global kinetic simulations. On the other hand, however, the two global simulations reproduce the similar collisionality dependencies of the NTV. With regard to the discrepancy of the theory and the global kinetic simulations, it has been recently pointed out that the effect of the magnetic field shear on the toroidal precession drift is not retained in the theory. In this study, we perform particle simulations, which is based on the local approximation, for the NTV. We discuss the cause of the discrepancy of the difference between the bounce-averaged local theory and the global kinetic simulations by investigating the effect of shear on the toroidal precession drift using the local particle simulations.