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Journal Articles

The Influence of the radial particle transport on the divertor plasma detachment

Hoshino, Kazuo; Shimizu, Katsuhiro; Takizuka, Tomonori*; Asakura, Nobuyuki; Nakano, Tomohide

Journal of Nuclear Materials, 463, p.573 - 576, 2015/08

 Times Cited Count:7 Percentile:22.72(Materials Science, Multidisciplinary)

Journal Articles

SOL-divertor plasma simulations introducing anisotropic temperature with virtual divertor model

Togo, Satoshi*; Takizuka, Tomonori*; Nakamura, Makoto; Hoshino, Kazuo; Ogawa, Yuichi*

Journal of Nuclear Materials, 463, p.502 - 505, 2015/08

 Times Cited Count:4 Percentile:43.49(Materials Science, Multidisciplinary)

A 1D SOL-divertor plasma simulation code introducing the anisotropic ion temperature with virtual divertor model has been developed. By introducing the anisotropic ion temperature directly, the second-derivative parallel ion viscosity term in the momentum transport equation can be excluded and the boundary condition at the divertor plate becomes unnecessary. In order to express the effects of the divertor plate and accompanying sheath implicitly, the virtual divertor model has been introduced which has an artificial sinks of particle, momentum and energy. The virtual divertor model makes the periodic boundary condition available. By using this model, SOL-divertor plasmas satisfying the Bohm condition has been successfully obtained. Also investigated are the dependence of the ion temperature anisotropy on the normalized mean free path of ion and the validity of the approximated parallel ion viscosity for the Braginskii expression and the limited one.

Journal Articles

Perspective of negative triangularity tokamak as fusion energy system

Kikuchi, Mitsuru; Medvedev, S.*; Takizuka, Tomonori*; Fasoli, A.*; Wu, Y.*; Diamond, P. H.*; Duan, X.*; Kishimoto, Yasuaki*; Hanada, Kazuaki*; 41 of others*

Europhysics Conference Abstracts (Internet), 39E, p.P4.179_1 - P4.179_4, 2015/06

Power and particle control in fusion reactor is quite a challenge and we have studied the negative triangularity tokamak (NTT) as an innovative concept to reduce the transient ELM heat load and the quasi steady-state heat load. A double-null NTT is stable to ideal MHD modes for a reactor relevant bN $$>$$ 3 while it is a magnetic hill configuration. In this paper, we report the configuration study of single-null NTT and its ideal MHD stability.

Journal Articles

A Possible breakthrough of power handling by plasma shaping in tokamak

Kikuchi, Mitsuru; Fasoli, A.*; Takizuka, Tomonori*; Diamond, P. H.*; Medvedev, S.*; Wu, Y.*; Duan, X.*; Kishimoto, Yasuaki*; Hanada, Kazuaki*; Pueschel, M. J.*; et al.

Proceedings of 8th IAEA Technical Meeting on Steady State Operation of Magnetic Fusion Devices (CD-ROM), 20 Pages, 2015/05

The standard D shaped H-mode operation showed excellent plasma confinement ut has important issues of transient and steady state heat flux. To solbe this issues, we proposed new scenario using plasma shaping as one of possible scenario of future tokamak reactor.

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

 Percentile:100(Physics, Fluids & Plasmas)

Journal Articles

Development of the backflow model for simplified impurity exhaust in Monte-Carlo calculation

Hoshino, Kazuo; Shimizu, Katsuhiro; Kawashima, Hisato; Takizuka, Tomonori*; Nakano, Tomohide; Ide, Shunsuke

Contributions to Plasma Physics, 54(4-6), p.404 - 408, 2014/06

 Times Cited Count:12 Percentile:28.31(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Integrated simulation study of ELM pacing by pellet injection in ITER

Hayashi, Nobuhiko; Aiba, Nobuyuki; Takizuka, Tomonori*; Oyama, Naoyuki

Contributions to Plasma Physics, 54(4-6), p.599 - 604, 2014/06

 Percentile:100(Physics, Fluids & Plasmas)

Journal Articles

Simple and fast Poisson solver with arbitrary boundary shape and condition for PIC simulation

Takizuka, Tomonori*; Azuma, Shuhei*; Fukuyama, Atsushi*; Shimizu, Katsuhiro

Contributions to Plasma Physics, 54(4-6), p.388 - 393, 2014/06

 Percentile:100(Physics, Fluids & Plasmas)

Particle-in-cell (PIC) simulations are the very powerful method to understand physics of edge plasmas in fusion devices. Poisson solver with a regular grid in a rectangular vessel is very fast, but it cannot simply be applicable to simulations in complicated divertor configuration. In this paper, a simple and fast Poisson solver with arbitrary boundary shape and condition for PIC simulation is proposed. Boundary points are essential for this Poisson solver, on which the charge density is appropriately given and the boundary condition is satisfied. For particle simulations in the open system, it is necessary to distinguish whether a traced particle moves freely or hits the wall boundary during a time step. A new method for PIC simulation to discriminate a particle position before the boundary or beyond the boundary is also presented.

Journal Articles

Kinetic modelling of divertor fluxes during ELMs in ITER

Hosokawa, Masanari*; Loarte, A.*; Huijsmans, G.*; Takizuka, Tomonori*; Hayashi, Nobuhiko

Europhysics Conference Abstracts (Internet), 38F, p.P5.003_1 - P5.003_4, 2014/06

Journal Articles

Divertor study on DEMO reactor

Hoshino, Kazuo; Asakura, Nobuyuki; Shimizu, Katsuhiro; Tokunaga, Shinsuke; Takizuka, Tomonori*; Someya, Yoji; Nakamura, Makoto; Uto, Hiroyasu; Sakamoto, Yoshiteru; Tobita, Kenji

Plasma and Fusion Research (Internet), 9(Sp.2), p.3403070_1 - 3403070_8, 2014/06

no abstracts in English

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

Negative triangularity as a possible tokamak scenario

Kikuchi, Mitsuru; Takizuka, Tomonori*; Furukawa, Masaru*

JPS Conference Proceedings (Internet), 1, p.015014_1 - 015014_4, 2014/03

Recent scaling of SOL e-folding length by Goldston shows pessimistic prediction to ITER and DEMO. This seems caused by the SOL acceleration mechanism found by Takizuka. In the negative D shaped plasma, this SOL acceleration may be significantly reduced. Negative D also has TEM eigen mode structure tilted poloidally and confinement in L mode is two times of L-mode. Based on these facts, we discuss possibility of negative D as a possible operation candidate of tokamak.

Journal Articles

A Simulation study of large power handling in the divertor for a Demo reactor

Asakura, Nobuyuki; Shimizu, Katsuhiro; Hoshino, Kazuo; Tobita, Kenji; Tokunaga, Shinsuke; Takizuka, Tomonori*

Nuclear Fusion, 53(12), p.123013_1 - 123013_15, 2013/12

 Times Cited Count:26 Percentile:11.47(Physics, Fluids & Plasmas)

Power exhaust scenario for 3 GW fusion reactor has been developed with enhancing the radiation loss from seeding impurity. Impurity transport and plasma detachment were simulated self-consistently under the Demo divertor condition using an integrated divertor code SONIC. Power handling with different seeding impurities showed that the total heat load, including the plasma transport and radiation, was reduced from 15 MW/m$$^{2}$$ to 10 MW/m$$^{2}$$ for the higher Z case, where both heat load components became comparable. Effects of a long-leg divertor were examined. Full detachment was obtained and peak heat load was decreased to 12 MW/m$$^{2}$$, where neutral load became comparable to the plasma and radiation load, which may be due to small flux expansion. Finally, plasma diffusion significantly affected the performance of the plasma detachment. Peak heat lard was reduced to 5 MW/m$$^{2}$$ well below engineering design level, with uniformly increasing the diffusion coefficient by the factor of two.

Journal Articles

Reduction of ELM energy loss by pellet injection for ELM pacing

Hayashi, Nobuhiko; Aiba, Nobuyuki; Takizuka, Tomonori*; Oyama, Naoyuki

Nuclear Fusion, 53(12), p.123009_1 - 123009_10, 2013/12

 Times Cited Count:4 Percentile:72.63(Physics, Fluids & Plasmas)

Journal Articles

Effect of resistivity profile on current decay time of initial phase of current quench in neon-gas-puff inducing disruptions of JT-60U

Kawakami, Sho*; Shibata, Yoshihide; Watanabe, Kiyomasa*; Ono, Noriyasu*; Isayama, Akihiko; Takizuka, Tomonori*; Kawano, Yasunori; Okamoto, Masaaki*

Physics of Plasmas, 20(11), p.112507_1 - 112507_6, 2013/11

 Times Cited Count:2 Percentile:86.48(Physics, Fluids & Plasmas)

According to an early work on the behavior of the plasma current decay in the JT-60U disruptive discharges caused by the radiative collapse with a massive neon-gas-puff, the increase of the internal inductance mainly determined the current decay time of plasma current during the initial phase of current quench. To investigate what determines the increase of the internal inductance, we focus attention on the relationship between the electron temperature (or the resistivity) profile and the time evolution of the current density profile, and carry out numerical calculations. As a result, we find the reason of the increase of the internal inductance: The current density profile at the start of the current quench is broader than an expected current density profile in the steady state, which is determined by the temperature (or resistivity) profile. The current density profile evolves into peaked one and the internal inductance is increasing.

Journal Articles

Hydrogen isotope effects on ITG scale length, pedestal and confinement in JT-60 H-mode plasmas

Urano, Hajime; Takizuka, Tomonori*; Aiba, Nobuyuki; Kikuchi, Mitsuru; Nakano, Tomohide; Fujita, Takaaki; Oyama, Naoyuki; Kamada, Yutaka; Hayashi, Nobuhiko; JT-60 Team

Nuclear Fusion, 53(8), p.083003_1 - 083003_8, 2013/08

 Times Cited Count:15 Percentile:26.34(Physics, Fluids & Plasmas)

Dependence of heat transport, edge pedestal and confinement on isotopic composition was investigated in conventional H-mode plasmas. Identical profiles for the electron density, electron temperature, and ion temperature were obtained for hydrogen and deuterium plasmas, whereas the required power clearly increased for hydrogen, which resulted in reduction of heat diffusivity for deuterium. The inverse of the ion-temperature-gradient (ITG) scale length which is required for a given ion heat diffusivity increased by a factor of approximately 1.2 for deuterium compared with that for hydrogen.

Journal Articles

Development of the transport-code framework for self-consistent predictions of rotation and the radial electric field

Honda, Mitsuru; Ide, Shunsuke; Takizuka, Tomonori*; Hayashi, Nobuhiko; Yoshida, Maiko; Yagi, Masatoshi; Fujita, Takaaki

Nuclear Fusion, 53(7), p.073050_1 - 073050_11, 2013/07

 Times Cited Count:14 Percentile:28.64(Physics, Fluids & Plasmas)

Journal Articles

Turbulence analyses of improved electron energy confinement in H-mode plasmas with gyrokinetic calculations

Narita, Emi; Honda, Mitsuru; Hayashi, Nobuhiko; Takizuka, Tomonori*; Ide, Shunsuke; Itami, Kiyoshi; Isayama, Akihiko; Fukuda, Takeshi*

Plasma and Fusion Research (Internet), 8, p.1403082_1 - 1403082_8, 2013/06

Journal Articles

Resonant magnetic perturbation for ELM suppression with helical ferritic steel inserts in tokamak DEMO reactor

Takizuka, Tomonori*; Oyama, Naoyuki; Fukuda, Takeshi*

Fusion Science and Technology, 63(1T), p.64 - 69, 2013/05

 Times Cited Count:1 Percentile:84.29(Nuclear Science & Technology)

Edge localized mode (ELM) must be eliminated which enhances the erosion of divertor plates in the H-mode operation of tokamak reactors. Suppression of ELM has been experimentally achieved by the resonant magnetic perturbation (RMP) with multipartite coils. In a DEMO reactor with strong neutron flux, however, it is desired the coils near the first wall not to be put in. We propose an innovative concept of the RMP for tokamak DEMO reactors without installing coils but inserting ferritic steels of the helical configuration. Helically perturbed magnetic field is naturally formed in the axisymmetric toroidal magnetic field through the helical ferritic steel inserts (FSIs). The perturbation amplitude in the plasma pedestal region can easily be set above several 10$$^{-4}$$ of the toroidal field strength in the DEMO reactor condition, which is enough for the RMP to suppress ELM.

Journal Articles

Reduction of ELM energy loss by pellet injection for ELM pacing

Hayashi, Nobuhiko; Aiba, Nobuyuki; Takizuka, Tomonori*; Oyama, Naoyuki

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

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