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Matsuoka, Seikichi; Idomura, Yasuhiro; Satake, Shinsuke*
Physics of Plasmas, 25(2), p.022510_1 - 022510_10, 2018/02
Times Cited Count：17 Percentile：74.87(Physics, Fluids & Plasmas)Global full-f gyrokinetic simulations, in which the gyrokinetic equation is solved based on the first principle without the scale separation with respect to the plasma distribution function, is attracting much attention in the plasma transport simulation studies. In this work, in order to apply a global full-f gyrokinetic simulation code GT5D to stellarator plasmas with complicated three-dimensional magnetic field configurations, we extend finite difference scheme of GT5D and develop a new interface code which incorporates the three-dimensional magnetic equilibria provided by a standard equilibrium code, VMEC. A series of benchmark calculations are carried out for the numerical verification of GT5D. It is successfully demonstrated that GT5D well reproduces results of a theoretical analysis and another global neoclassical transport code.
Kanno, Ryutaro*; Nunami, Masanori*; Satake, Shinsuke*; Matsuoka, Seikichi; Takamaru, Hisanori*
Nuclear Fusion, 58(1), p.016033_1 - 016033_7, 2018/01
Times Cited Count：0 Percentile：0.01(Physics, Fluids & Plasmas)The electron heat transport in a torus plasma which involves a radially-bounded ergodic region, where flux surfaces are partially destroyed by perturbative magnetic fields, is studied. In this paper, we have demonstrated that the radial heat conduction by the particles' parallel motion is reduced by trapped particles.
Matsuoka, Seikichi; Idomura, Yasuhiro; Satake, Shinsuke*
Physics of Plasmas, 24(10), p.102522_1 - 102522_9, 2017/10
Times Cited Count：4 Percentile：21.74(Physics, Fluids & Plasmas)In axisymmetric tokamak plasmas, effects of three-dimensional non-axisymmetric magnetic field perturbations caused by error fields etc. 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 in predicting the collisional viscosity driven by the perturbation between a theoretical bounce-averaged model and a global kinetic simulation. Clarifying the cause of the discrepancy by understanding the underlying mechanism is a key issue to establish a reliable basis for the NTV predictions. In this work, we perform two different kinds of global kinetic simulations for the NTV. As a result, it is first demonstrated that the discrepancy arises owing to the following two mechanisms related to the global particle orbit; (1) the effective magnitude of the perturbation becomes weak due to the loss of the resonant orbit, and (2) the phase mixing along the orbit arises and generates fine scale structures, resulting the damping of the NTV.
Huang, B.*; Satake, Shinsuke*; Kanno, Ryutaro*; Sugama, Hideo*; Matsuoka, Seikichi
Physics of Plasmas, 24(2), p.022503_1 - 022503_19, 2017/02
Times Cited Count：11 Percentile：54.14(Physics, Fluids & Plasmas)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.
Kanno, Ryutaro*; Nunami, Masanori*; Satake, Shinsuke*; Matsuoka, Seikichi; Takamaru, Hisanori*
Contributions to Plasma Physics, 56(6-8), p.592 - 597, 2016/08
Times Cited Count：2 Percentile：11.54(Physics, Fluids & Plasmas)A drift-kinetic 
simulation code is developed for estimating collisional transport in quasi-steady state of toroidal plasma affected by resonant magnetic perturbations and radial electric field. In this paper, validity of the code is confirmed through several test calculations. It is found that radial electron flux is reduced by positive radial-electric field, although radial diffusion of electron is strongly affected by chaotic field-lines under an assumption of zero electric field.
Sugama, Hideo*; Matsuoka, Seikichi; Satake, Shinsuke*; Kanno, Ryutaro*
Physics of Plasmas, 23(4), p.042502_1 - 042502_11, 2016/04
Times Cited Count：7 Percentile：32.55(Physics, Fluids & Plasmas)A novel radially local approximation of the drift kinetic equation is presented. The new drift kinetic equation that includes both 
and tangential magnetic drift terms is written in the conservative form and it has favorable properties for numerical simulation that any additional terms for particle and energy sources are unnecessary for obtaining stationary solutions under the radially local approximation. These solutions satisfy the intrinsic ambipolarity condition for neoclassical particle fluxes in the presence of quasisymmetry of the magnetic field strength. Also, another radially local drift kinetic equation is presented, from which the positive definiteness of entropy production due to neoclassical transport and Onsager symmetry of neoclassical transport coefficients are derived while it sacrifices the ambipolarity condition for neoclassical particle fluxes in axisymmetric and quasi-symmetric systems.
Okamoto, Masao*; Hamamatsu, Kiyotaka; Murakami, Sadayoshi*; Nakajima, Noriyoshi*
Purazuma, Kaku Yugo Gakkai-Shi, 77(6), p.536 - 546, 2001/06
no abstracts in English
Inoue, Haruyuki*; Homma, Yuki; Yamoto, Shohei*; Hatayama, Akiyoshi*
no journal, ,
no abstracts in English
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.
Matsuoka, Seikichi; Idomura, Yasuhiro; Satake, Shinsuke*
no journal, ,
Effects of non-axisymmetric magnetic field perturbations in tokamak devices in which the magnetic field is axisymmetric have attracted much attention. The non-axisymmetric perturbations produces the so-called neoclassical toroidal viscosity (NTV), which is caused by collisional processes in a plasma. The NTV can make influence on the plasma rotation, which plays a key role in controlling a confinement performance and instabilities. Recently, however, it was pointed out that severe discrepancy exists with regard to the evaluation of the NTV between a Superbanana-plateau theory based on the bounce-averaged particle orbit and a global kinetic simulation. Clarifying physical mechanisms that causes the discrepancy is crucial for precise evaluation/prediction of the NTV. In this work, we perform two different types of global kinetic simulations, of which physical and numerical models are quite different from each other to resolve the issue. As a result, it is demonstrated that the discrepancy arises owing to the lack of the following two mechanisms in the theory; (1) insufficient resonance condition with regard to the precession drift, and (2) the transition processes of the particle orbit caused by the non-axisymmetric perturbations.
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. 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 owing to the following two mechanisms; (1) resonant structures predicted in the bounce-averaged model disappear due to the large particle orbit in the global kinetic simulations, and (2) fine scale structures are generated in the velocity space in the global kinetic simulations.
Matsuoka, Seikichi; Idomura, Yasuhiro; Satake, Shinsuke*
no journal, ,
Effects of non-axisymmetric magnetic field perturbations caused by error fields and external perturbations have attracted much attention in many axisymmetric tokamak devices such as JT-60 and ITER from the view point of the control of the plasma confinement performance and instabilities. The non-axisymmetric perturbations cause the neoclassical toroidal viscosity (NTV), and establishing a reliable basis for the evaluation/prediction of the NTV becomes important. Recent studies pointed out that the qualitative discrepancy with regard to the evaluation of the NTV exist between a widely-used superbanana-plateau theory based on the bounce-averaged model and a global kinetic simulation. Hence it is crucial to clarify the cause of the discrepancy. In this work, we perform two different 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 in the theory; one is the insufficient resonance condition with regard to the precession drift, and the other is the transition processes of the particle orbit caused by the non-axisymmetric perturbations.
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.
Huang, B.*; Satake, Shinsuke*; Kanno, Ryutaro*; Matsuoka, Seikichi
no journal, ,
The bootstrap current, or the parallel flow in a toroidal plasma is described by the neoclassical transport theory. In recent studies, it was pointed out that numerical models of the radially-local neoclassical transport, in which the radial drift of particles is entirely neglected, can be classified according to approximations used in the models. In this work, we perform a series of benchmarks of the parallel flow for the LHD, HSX, and W7-X by using three types of the local neoclassical transport simulations models. It is shown that the magnetic drift tangential to a flux surface significantly changes the parallel flow when the radial electric field is weak in a low-collisional LHD plasma. We also find that the effect of the tangential drift becomes small in other magnetic configurations of HSX and W7-X.
Matsuoka, Seikichi; Idomura, Yasuhiro; Satake, Shinsuke*
no journal, ,
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.
Matsuoka, Seikichi; Idomura, Yasuhiro; Satake, Shinsuke*
no journal, ,
Effects of non-axisymmetric magnetic field perturbations on plasma transport 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 in predicting the collisional viscosity driven by the perturbation 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.
Matsuoka, Seikichi; Idomura, Yasuhiro; Satake, Shinsuke*
no journal, ,
Effects of non-axisymmetric magnetic field perturbations on plasma transport 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 in predicting the collisional viscosity driven by the perturbation between a theoretical bounce-averaged model and a global kinetic simulation. Clarifying the cause of the discrepancy by understanding the underlying mechanism is a key issue to establish a reliable basis for the NTV predictions. In this work, we perform two different kinds of global kinetic simulations for the NTV. As a result, it is first demonstrated that the discrepancy arises owing to the following two mechanisms; (1) the effective magnitude of the perturbation becomes weak due to the finite orbit width of the global particle orbit, and (2) the velocity space structures are damped by the phase mixing along the global particle orbit.
Idomura, Yasuhiro; Obrejan, K.; Honda, Mitsuru*
no journal, ,
Global neoclassical transport analyses of tungsten impurity are conducted using the global full-f gyrokinetic code GT5D, and the results are compared against local neoclassical transport theory by Hirshman-Sigmar. Systematic scans of the plasma size and the temperature gradient showed that theory and simulations show quantitative agreements when the plasma size is large enough. However, at smaller plasma sizes, it is found that steep temperature gradients enhance their differences, and theory overestimates the thermal screening effect of tungsten transport.
Idomura, Yasuhiro; Obrejan, K.*; Asahi, Yuichi; Honda, Mitsuru*
no journal, ,
Transport mechanisms of tracer impurities in the ion temperature gradient driven (ITG) turbulence are studied using the global full-f gyrokinetic code GT5D, and it is found that neoclassical particle transport is greatly enhanced by an interaction with the ITG turbulence. The radial electric field grows by turbulent bulk particle transport driven by the ITG turbulence. A compression effect of the resulting E
B flows generates up-down asymmetric density perturbations, which are coupled with the magnetic drift to enhance neoclassical particle transport. This effect does not work for the temperature, and selectively enhances only particle transport.
