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Journal Articles

Progress report of Japanese simulation research projects using the high-performance computer system Helios in the International Fusion Energy Research Centre

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.

Journal Articles

Report of ITPA TG Meetings, 52

Shinohara, Koji; Hayashi, Nobuhiko; Isayama, Akihiko; Miyato, Naoaki; Urano, Hajime; Aiba, Nobuyuki

Purazuma, Kaku Yugo Gakkai-Shi, 91(12), p.797 - 800, 2015/12

no abstracts in English

Journal Articles

Effects of toroidal rotation shear and magnetic shear on thermal and particle transport in plasmas with electron cyclotron heating on JT-60U

Yoshida, Maiko; Honda, Mitsuru; Narita, Emi*; Hayashi, Nobuhiko; Urano, Hajime; Nakata, Motoki; Miyato, Naoaki; Takenaga, Hidenobu; Ide, Shunsuke; Kamada, Yutaka

Nuclear Fusion, 55(7), p.073014_1 - 073014_9, 2015/07

 Times Cited Count:13 Percentile:61.42(Physics, Fluids & Plasmas)

Conditions without the increases in the thermal and particle transport with ECH have been experimentally investigated in positive magnetic shear (PS), weak magnetic shear (WS) and reversed magnetic shear (RS) plasmas with internal transport barriers (ITBs) on JT-60U. The ion heat diffusivity around an internal transport barrier in the ion temperature ($$T_{rm i}$$-ITB) remains constant with ECH when a large negative toroidal rotation shear is formed before the ECH. The condition does not depend on the electron to ion temperature ratio ($$T_{rm e}$$/$$T_{rm i}$$) and ECH power. The electron heat diffusivity around a $$T_{rm e}$$-ITB stays constant with ECH when the magnetic shear is negative around the Te-ITB region. Effective particle transport remains constant or reduces during ECH under the condition of negative magnetic shear.

Journal Articles

Cross-scale interactions between electron and ion scale turbulence in a tokamak plasma

Maeyama, Shinya*; Idomura, Yasuhiro; Watanabe, Tomohiko*; Nakata, Motoki*; Yagi, Masatoshi; Miyato, Naoaki; Ishizawa, Akihiro*; Nunami, Masanori*

Physical Review Letters, 114(25), p.255002_1 - 255002_5, 2015/06

 Times Cited Count:68 Percentile:95.12(Physics, Multidisciplinary)

Multiscale gyrokinetic turbulence simulations with the real ion-to-electron mass ratio and $$beta$$ value are realized for the first time, where the $$beta$$ value is given by the ratio of plasma pressure to magnetic pressure and characterizes electromagnetic effects on microinstabilities. Numerical analysis at both the electron scale and the ion scale is used to reveal the mechanism of their cross-scale interactions. Even with the real- mass scale separation, ion-scale turbulence eliminates electron-scale streamers and dominates heat transport, not only of ions but also of electrons. When the ion-scale modes are stabilized by finite-$$beta$$ effects, the contribution of the electron-scale dynamics to the turbulent transport becomes non-negligible and turns out to enhance ion-scale turbulent transport.

Journal Articles

On push-forward representations in the standard gyrokinetic model

Miyato, Naoaki; Yagi, Masatoshi; Scott, B. D.*

Physics of Plasmas, 22(1), p.012103_1 - 012103_9, 2015/01

 Times Cited Count:4 Percentile:23.73(Physics, Fluids & Plasmas)

Two representations of fluid moments, which are called push-forward representations, are compared in the standard electrostatic gyrokinetic model. In the conventional representation the gyro-center part appears as the pull-back transformation of the gyro-center distribution function which contains scalar functions generating the gyro-center transformation. Usually only the lowest order solution of the generating function at first order is considered. This is true in explicitly deriving representations of scalar fluid moments with polarization terms. However, higher-order solutions are needed to derive finite Larmor radius terms of particle flux including the polarization flux from the conventional representation. On the other hand, the lowest order solution is sufficient for the other representation in which the gyro-center part is combined with the guiding-center one and the pull-back transformation of the distribution function does not appear.

Journal Articles

Effect of ion temperature gradient driven turbulence on the edge-core connection for transient edge temperature sink

Miyato, Naoaki

Plasma and Fusion Research (Internet), 9, p.1203148_1 - 1203148_3, 2014/12

Ion temperature gradient (ITG) driven turbulence simulation with a transient edge temperature sink which is localized in the poloidal plane is performed using a global Landau-fluid code in the electrostatic limit. Pressure perturbations with $$(m, n)$$=$$(pm 1, 0)$$ input by the edge sink, which are responsible for the nonlocal transport found in reduced magnetohydrodynamic (RMHD) simulation, are dissipated by the ITG turbulence in the core, where $$m$$ and $$n$$ are poloidal and toroidal mode numbers, respectively. Hence, the ITG turbulence tends to prevent the $$(pm 1, 0)$$ pressure perturbations connecting the core region with the edgeand thereby the nonlocal plasma response/transport of a kind observed in the RMHD simulation.

Journal Articles

Report on ITPA meetings, 47

Isayama, Akihiko; Urano, Hajime; Miyato, Naoaki; Ide, Shunsuke; Asakura, Nobuyuki; Shinohara, Koji

Purazuma, Kaku Yugo Gakkai-Shi, 90(12), p.830 - 833, 2014/12

no abstracts in English

Journal Articles

Extension of kinetic-magnetohydrodynamic model to include toroidal rotation shear effect and its application to stability analysis of resistive wall modes

Shiraishi, Junya; Miyato, Naoaki; Matsunaga, Go; Honda, Mitsuru; Hayashi, Nobuhiko; Ide, Shunsuke

Proceedings of 25th IAEA Fusion Energy Conference (FEC 2014) (CD-ROM), 8 Pages, 2014/10

Extension of the kinetic-magnetohydrodynamic (MHD) model is presented to include toroidal rotation shear effect for the first time. The sheared rotation is introduced through generalization of the guiding center Lagrangian, yielding two additional terms in a quadratic form of mode-particle resonance. Additionally, another new term is introduced by using the equilibrium distribution function with rotation effect. These three terms are overlooked in conventional models. The new model is applied to stability analysis of resistive wall modes (RWMs) successfully. Numerical results show that the rotation shear reduces RWM growth rates further, which is consistent with experimental results.

Journal Articles

Effects of centrifugal modification of magnetohydrodynamic equilibrium on resistive wall mode stability

Shiraishi, Junya; Aiba, Nobuyuki; Miyato, Naoaki; Yagi, Masatoshi

Nuclear Fusion, 54(8), p.083008_1 - 083008_8, 2014/08

 Times Cited Count:8 Percentile:44.28(Physics, Fluids & Plasmas)

Toroidal rotation effects are self-consistently taken into account not only in the linear magnetohydrodynamic (MHD) stability analysis but also in the equilibrium calculation. The MHD equilibrium computation is affected by centrifugal force due to the toroidal rotation. To study the toroidal rotation effects on resistive wall modes (RWMs), a new code has been developed. The RWMaC modules, which solve the electromagnetic dynamics in vacuum and the resistive wall, have been implemented in the MINERVA code, which solves the Frieman-Rotenberg equation that describes the linear ideal MHD dynamics in a rotating plasma. It is shown that modification of MHD equilibrium by the centrifugal force significantly reduces growth rates of RWMs. Moreover, it can open a stable window which does not exist under the assumption that the rotation affects only the linear dynamics.

Journal Articles

Edge radial electric field formation after the L-H transition on JT-60U

Kamiya, Kensaku; Matsunaga, Go; Honda, Mitsuru; Miyato, Naoaki; Urano, Hajime; Kamada, Yutaka; Ida, Katsumi*; Ito, Kimitaka*; JT-60 Team

Contributions to Plasma Physics, 54(4-6), p.591 - 598, 2014/06

 Times Cited Count:6 Percentile:35.23(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Simulation study of nonlocal transport from edge to core in tokamak plasmas

Yagi, Masatoshi; Matsuyama, Akinobu; Miyato, Naoaki; Takizuka, Tomonori*

Contributions to Plasma Physics, 54(4-6), p.363 - 367, 2014/06

 Times Cited Count:0 Percentile:0.01(Physics, Fluids & Plasmas)

Journal Articles

Comparison between kinetic-ballooning-mode-driven turbulence and ion-temperature-gradient-driven turbulence

Maeyama, Shinya; Ishizawa, Akihiro*; Watanabe, Tomohiko*; Nakata, Motoki; Miyato, Naoaki; Yagi, Masatoshi; Idomura, Yasuhiro

Physics of Plasmas, 21(5), p.052301_1 - 052301_12, 2014/05

 Times Cited Count:11 Percentile:56.05(Physics, Fluids & Plasmas)

Journal Articles

Simulation study on nonlocal transport for peripheral density source

Yagi, Masatoshi; Miyato, Naoaki; Matsuyama, Akinobu; Takizuka, Tomonori*

Plasma and Fusion Research (Internet), 9, p.3403030_1 - 3403030_4, 2014/04

Journal Articles

On kinetic resistive wall mode theory with sheared rotation

Shiraishi, Junya; Miyato, Naoaki; Matsunaga, Go

Plasma and Fusion Research (Internet), 9, p.3403027_1 - 3403027_4, 2014/04

To investigate the rotation shear effect on the RWM (Resistive Wall Mode) stability, we generalize the formalism of kinetic RWM theory to include a general equilibrium rotation. Starting from the guiding-center Lagrangian with the non-uniform rotation, we generalize the energy functional associated with the drift-kinetic resonance. By the generalized kinetic energy functional, we derive a new dispersion relation in the large aspect ratio limit. Numerical analysis of the new dispersion relation indicates that the rotation shear stabilizes the RWMs as observed in experiments

Journal Articles

Kinetic ballooning mode turbulence simulation based on electromagnetic gyrokinetics

Maeyama, Shinya; Ishizawa, Akihiro*; Watanabe, Tomohiko*; Nakata, Motoki; Miyato, Naoaki; Idomura, Yasuhiro

Plasma and Fusion Research (Internet), 9, p.1203020_1 - 1203020_3, 2014/03

Journal Articles

Temporal and spatial responses of temperature, density and rotation to electron cyclotron heating in JT-60U

Yoshida, Maiko; Ide, Shunsuke; Takenaga, Hidenobu; Honda, Mitsuru; Urano, Hajime; Kobayashi, Takayuki; Nakata, Motoki; Miyato, Naoaki; Kamada, Yutaka

Nuclear Fusion, 53(8), p.083022_1 - 083022_10, 2013/07

 Times Cited Count:6 Percentile:30.65(Physics, Fluids & Plasmas)

Time and special responses of electron channels and ion channels with central electron cyclotron heating (ECH) have been investigated in JT-60U positive shear H-mode and internal transport barrier (ITB) plasmas. The ion temperature reduces with ECH after the increase in the electron temperature where an increase in the ion heat transport with ECH accompanies an increase in the electron thermal transport. The core electron density decreases with ECH when the density profile is peaked before ECH injection. The counter intrinsic rotation with ECH is identified using H-mode plasmas with small torque input (BAL-NBI). The counter intrinsic rotation is generated after the increase in the electron temperature and correlates with the change in the electron temperature with ECH around the EC deposition. Time scale of the change in the toroidal rotation velocity is about 90-200 ms around the ECH deposition and the time scale is longer compared to those in $$T$$$$_{rm e}$$ and $$T$$$$_{rm i}$$.

Journal Articles

On the Gyrokinetic model in long wavelength regime

Miyato, Naoaki; Scott, B. D.*; Yagi, Masatoshi

Plasma Physics and Controlled Fusion, 55(7), p.074011_1 - 074011_6, 2013/07

 Times Cited Count:6 Percentile:30.65(Physics, Fluids & Plasmas)

Journal Articles

Stabilization of resistive wall modes by magnetohydrodynamic equilibrium change induced by plasma toroidal rotation

Shiraishi, Junya; Aiba, Nobuyuki; Miyato, Naoaki; Yagi, Masatoshi

Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 8 Pages, 2013/03

Effects of plasma toroidal rotation are self-consistently taken into account not only in the magnetohydrodynamic (MHD) stability analysis but also in the equilibrium calculation. To study the effects of toroidal rotation on resistive wall modes (RWMs), a new code has been developed. The RWMaC modules, which solve the electromagnetic dynamics in vacuum and the resistive wall, have been implemented in the MINERVA code, which solves the Frieman-Rotenberg equation that describes the linear ideal MHD in a rotating plasma. It is shown for the first time that MHD equilibrium change induced by toroidal rotation significantly reduces the growth rates of RWMs. Moreover, it can open the stable window which does not exist under the assumption that the rotation affects only the linear dynamics. The rotation modifies the equilibrium pressure, current density, and mass density profiles, which results in the change of the potential energy including rotational effects.

Journal Articles

Modifications to the edge radial electric field by angular momentum injection in JT-60U and their implication for pedestal transport

Kamiya, Kensaku; Honda, Mitsuru; Miyato, Naoaki; Urano, Hajime; Yoshida, Maiko; Sakamoto, Yoshiteru; Matsunaga, Go; Oyama, Naoyuki; Koide, Yoshihiko; Kamada, Yutaka; et al.

Nuclear Fusion, 52(11), p.114010_1 - 114010_12, 2012/10

 Times Cited Count:10 Percentile:45.75(Physics, Fluids & Plasmas)

Depending on the direction of the external tangential momentum input, substantial changes in not only toroidal but also poloidal flows for the carbon impurity ions are observed at around the $$E$$$$_{r}$$-well region. The shear in the edge $$E$$$$_{r}$$ becomes wider in the co-NBI case, while the edge $$E$$$$_{r}$$-well becomes deeper in the counter-NBI case.

Journal Articles

Observation of energetic particle driven axisymmetric mode in the JT-60U tokamak

Matsunaga, Go; Kamiya, Kensaku; Shinohara, Koji; Miyato, Naoaki; Kojima, Atsushi; Bierwage, A.; JT-60 Team

Europhysics Conference Abstracts (Internet), 36F, p.P2.062_1 - P2.062_4, 2012/00

104 (Records 1-20 displayed on this page)