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Matsuoka, Seikichi*; Sugama, Hideo*; Idomura, Yasuhiro
Physics of Plasmas, 28(6), p.064501_1 - 064501_5, 2021/06
Times Cited Count：4 Percentile：23.33(Physics, Fluids & Plasmas)The improved model collision operator proposed by Sugama et al., which can recover the friction-flow relation of the linearized Landau collision operator, is newly implemented in a global full- f gyrokinetic simulation code, GT5D, and collisional transport simulations of a single ion species plasma in a tokamak are performed over the wide collisionality regime. The improved operator is verified to reproduce the theoretical collisional thermal diffusivity precisely in the high collisionality regime, where the friction-flow relation of higher accuracy is required than in the lower collisional regime. In addition, it is found in all collisionality regimes that the higher accuracy of the collisional thermal diffusivity and the parallel flow coefficient is obtained by the improved operator, demonstrating that collisional processes described by the linearized Landau collision operator is correctly retained.
Matsuoka, Seikichi; Idomura, Yasuhiro; Satake, Shinsuke*
Physics of Plasmas, 25(2), p.022510_1 - 022510_10, 2018/02
Times Cited Count：22 Percentile：72.49(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：0.00(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：17.73(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：45.57(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：3 Percentile：14.12(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.
Idomura, Yasuhiro; Asahi, Yuichi; Ina, Takuya; Matsuoka, Seikichi
Proceedings of 24th International Congress of Theoretical and Applied Mechanics (ICTAM 2016), p.3106 - 3107, 2016/08
Turbulent transport in fusion plasmas is one of key issues in ITER. To address this issue via the five dimensional (5D) gyrokinetic model, a novel computing technique is developed, and strong scaling of the Gyrokinetic Toroidal 5D Eulerian code GT5D is improved up to 
million cores on the K-computer. The computing technique consists of multi-dimensional/multi-layer domain decomposition, overlap of communication and computation, and optimization of computing kernels for multi-core CPUs. The computing power enabled us to study ITER relevant issues such as the plasma size scaling of turbulent transport. Towards the next generation burning plasma turbulence simulations, the physics model is extended including kinetic electrons and multi-species ions, and computing kernels are further optimized for the latest many-core architectures.
Sugama, Hideo*; Matsuoka, Seikichi; Satake, Shinsuke*; Kanno, Ryutaro*
Physics of Plasmas, 23(4), p.042502_1 - 042502_11, 2016/04
Times Cited Count：8 Percentile：36.10(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.
Ishizawa, Akihiro*; Idomura, Yasuhiro; Imadera, Kenji*; Kasuya, Naohiro*; Kanno, Ryutaro*; Satake, Shinsuke*; Tatsuno, Tomoya*; Nakata, Motoki*; Nunami, Masanori*; Maeyama, Shinya*; et al.
Purazuma, Kaku Yugo Gakkai-Shi, 92(3), p.157 - 210, 2016/03
The high-performance computer system Helios which is located at The Computational Simulation Centre (CSC) in The International Fusion Energy Research Centre (IFERC) started its operation in January 2012 under the Broader Approach (BA) agreement between Japan and the EU. The Helios system has been used for magnetised fusion related simulation studies in the EU and Japan and has kept high average usage rate. As a result, the Helios system has contributed to many research products in a wide range of research areas from core plasma physics to reactor material and reactor engineering. This project review gives a short catalogue of domestic simulation research projects. First, we outline the IFERC-CSC project. After that, shown are objectives of the research projects, numerical schemes used in simulation codes, obtained results and necessary computations in future.
Matsuoka, Seikichi*; Satake, Shinsuke*; Idomura, Yasuhiro; Imamura, Toshiyuki*
Proceedings of Joint International Conference on Mathematics and Computation, Supercomputing in Nuclear Applications and the Monte Carlo Method (M&C + SNA + MC 2015) (CD-ROM), 13 Pages, 2015/04
The quality and performance of a parallel pseudo-random number generator (PRNG), KMATH_RANDOM, are investigated using a Monte Carlo particle simulation code for the plasma transport. The library is based on Mersenne Twister with jump routines and provides a numerical tool which is suitable and easy-to-use on massively parallel supercomputers such as K-computer. The library enables the particle code to increase the parallelization up to several thousand processes without loosing the quality and performance of the PRNG. As a result, the particle code can use large amounts of random numbers, which results in removing unphysical phenomena caused by a numerical noise.
flows in helical plasmasWatanabe, Tomohiko*; Nunami, Masanori*; Sugama, Hideo*; Satake, Shinsuke*; Matsuoka, Seikichi*; Ishizawa, Akihiro*; Maeyama, Shinya; Tanaka, Kenji*
Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 8 Pages, 2012/10
Matsuoka, Seikichi; Idomura, Yasuhiro; Satake, Shinsuke*
no journal, ,
Recently, full-f simulations, in which the gyrokinetic equation is solved based on the first principle to obtain the time development of the total plasma distribution function, attracted much attention in the plasma transport study. Rich physics has been revealed by the simulations in axisymmetric tokamak plasmas such as JT-60 and ITER. However, no such full-f gyrokinetic simulations in three-dimensional magnetic field equilibria such as stellarators and/or helical devices have been reported so far due to their complicated magnetic field geometries which requires more computational resources. In this work, we extend a full-f gyrokinetic simulation code, GT5D, to treat three-dimensional magnetic equilibria by modifying its coordinate system, and develop a new interface between GT5D and VMEC, where VMEC is a widely used numerical tool to construct a three-dimensional magnetic equilibria. In the presentation, we give a presentation of the current status of the code development, numerical scheme used in the code, and simulation results.
Matsuoka, Seikichi; Idomura, Yasuhiro
no journal, ,
Recently, full-f gyrokinetic simulations, in which the total plasma distribution is evolved based on the first principle, attracted much attention in the plasma transport study. Rich physics has been revealed by the simulations in axisymmetric tokamak plasmas such as JT-60 and ITER. However, no full-f gyrokinetic simulations in non-axisymmetric, or three-dimensional magnetic field equilibria such as stellarators and/or helical devices have been reported so far due to their complicated magnetic field geometries which requires more computational resources. In this work, we extend a full-f gyrokinetic simulation code, GT5D, to treat three-dimensional magnetic equilibria by modifying its coordinates, and develop a new interface between GT5D and VMEC, where VMEC is a numerical tool to construct a three-dimensional magnetic equilibria. In the presentation, we present benchmark results as a numerical verification of GT5D+VMEC by comparing the collisional (neoclassical) transport.
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.
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.
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 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; Honda, Mitsuru*; Satake, Shinsuke*; Suzuki, Yasuhiro*
no journal, ,
Effects of three-dimensional magnetic perturbation arising from e.g. error fields due to the imperfect coil manufacturing and installations, have attracted much attention in transport studies in axisymmetric tokamak plasmas. In this work, we performed global full-f gyrokinetic simulations for a JT-60U equilibrium which involve the three-dimensional perturbation by using experimental equilibrium version of a global full-f gyrokinetic simulation code, GT5D. Quantitative agreement of the neoclassical transport and the ambipolar radial electric field between GT5D and the existing couple analysis model is confirmed. And it is also confirmed that the neoclassical toroidal viscosity induced by the perturbation shows qualitative agreement with the couple analysis model. Furthermore, the numerical cost for the experimental analysis can be greatly reduced by using GT5D.
Matsuoka, Seikichi*; Idomura, Yasuhiro; Satake, Shinsuke*; Honda, Mitsuru*; Suzuki, Yasuhiro*
no journal, ,
A Gyrokinetic Toroidal 5D full-f Eulerian code GT5D is extended for three dimensional magnetic configurations such as stellarators and tokamaks with perturbed magnetic fields. An interface program for three dimensional equilibrium magnetic configuration code VMEC is constructed to generate a vector potential used in GT5D. The developed code is verified through benchmark calculations of neoclassical transport and geodesic acoustic modes in a Large Helical Device configuration. The results show quantitative agreements against the three dimensional delta-f particle code FORTEC3D.
Idomura, Yasuhiro; Obrejan, K.; Asahi, Yuichi*; Matsuoka, Seikichi*
no journal, ,
To enable low cost experimental data analyses Transient plasma responses due to modulated electron heating are investigated in numerical experiments of ion temperature gradient driven trapped electron mode turbulence using gyrokinetic full-f Eulerian code GT5D. It is found that even with electron heating without particle and momentum sources such as electron cyclotron resonance heating, dominant turbulence is changed from ion turbulence to electron turbulence due to changes of the electron temperature gradient and the temperature ratio, and the resulting turbulent transport produces responses of density and rotation profiles.
