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Journal Articles

Zonal flow and GAM dynamics and associated transport characteristics in reversed shear tokamaks

Miyato, Naoaki; Kishimoto, Yasuaki; Li, J.*

Journal of Plasma Physics, 72(6), p.821 - 824, 2006/12

 Times Cited Count:0 Percentile:100(Physics, Fluids & Plasmas)

Zonal flow behaviour and its effect on turbulent transport in reversed shear tokamaks are investigated by global nonlinear simulation of ion temperature gradient driven turbulence. When safety factor $$q$$ is reduced, zonal flows in a minimum $$q$$ region change from oscillatory ones to stationary ones and suppress the turbulent transport effectively. This result indicates that the change of zonal flow behaviour in the minimum $$q$$ region may trigger the formation of ion transport barriers.

Journal Articles

Observation of the interaction between the geodesic acoustic mode and ambient fluctuation in the JFT-2M tokamak

Ido, Takeshi*; Miura, Yukitoshi; Hoshino, Katsumichi; Kamiya, Kensaku; Hamada, Yasuji*; Nishizawa, Akimitsu*; Kawasumi, Yoshiaki*; Ogawa, Hiroaki; Nagashima, Yoshihiko*; Shinohara, Koji; et al.

Nuclear Fusion, 46(5), p.512 - 520, 2006/05

 Times Cited Count:77 Percentile:6.31(Physics, Fluids & Plasmas)

The electrostatic fluctuation spectrum and the fluctuation-induced particle flux of the JFT-2M tokamak were estimated using the hevy ion beam probe (HIBP) measurement. A geodesic acoustic mode (GAM) of the frequency about15kHz was identified in the L-mode. The GAM has its peak at about 3cm inside of the separatrix with the electric field of about 1.4kV/m. The estimated turbulent particle flux is found to be intermittent. It is found that the density fluctuation is modulated by the GAM in the wide frequency range and the coherence analysis shows that the flucruation-induced particle flux is partially contributed by the GAM. In the H-mode the GAM disappears and the fluctuation and the flux is much decreased.The mechanism of the large burst-like flux in the L-mode is not understood yet and left as the future problem.

Journal Articles

Physics of strong internal transport barriers in JT-60U reversed-magnetic-shear plasmas

Hayashi, Nobuhiko; Takizuka, Tomonori; Sakamoto, Yoshiteru; Fujita, Takaaki; Kamada, Yutaka; Ide, Shunsuke; Koide, Yoshihiko

Plasma Physics and Controlled Fusion, 48(5A), p.A55 - A61, 2006/05

 Times Cited Count:7 Percentile:72.7(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Profile formation and sustainment of autonomous tokamak plasma with current hole configuration

Hayashi, Nobuhiko; Takizuka, Tomonori; Ozeki, Takahisa

Nuclear Fusion, 45(8), p.933 - 941, 2005/08

 Times Cited Count:13 Percentile:54.97(Physics, Fluids & Plasmas)

We have investigated profile formation and sustainment of current hole (CH) plasma by 1.5D transport simulations with current limit model inside CH based on Axisymmetric Tri-Magnetic-Islands equilibrium. Sharp reduction of anomalous transport in RS region can reproduce JT-60U experiments. The transport becomes neoclassical-level in RS region, which results in autonomous profile formation of ITB and CH through large bootstrap current. ITB width determined by neoclassical-level transport agrees with that in JT-60U. Energy confinement inside ITB agrees with JT-60U scaling. The scaling means that core plasma inside ITB is governed by MHD equilibrium limit, i.e., autonomous limitation of energy confinement. The plasma with large CH is sustained with full current drive by bootstrap current. The plasma with small CH and small bootstrap current fraction shrinks due to penetration of inductive current. This shrink is prevented and CH size can be controlled by appropriate external CD. CH plasma is found to respond autonomically to external CD. Application of CH plasma to reactor is discussed.

Journal Articles

Profile formation and sustainment of autonomous tokamak plasma with current hole configuration

Hayashi, Nobuhiko; Takizuka, Tomonori; Ozeki, Takahisa

Proceedings of 20th IAEA Fusion Energy Conference (FEC 2004) (CD-ROM), 8 Pages, 2004/11

Profile formation and sustainment of tokamak plasmas with current hole (CH) have been investigated by using 1.5D transport simulations. A current limit model inside CH based on the Axisymmetric Tri-Magnetic-Islands equilibrium is introduced. We found that the sharp reduction of anomalous transport in the reversed-shear (RS) region can reproduce JT-60U experiment. The transport becomes neoclassical-level in RS region, which results in the autonomous formation of internal transport barrier (ITB) and CH through large bootstrap current. ITB width determined by neoclassical-level transport agrees with that in JT-60U. Energy confinement inside ITB agrees with JT-60U scaling, which means autonomous limitation of energy confinement. The plasma with large CH is sustained with the full current drive by bootstrap current. The plasma with small CH and small bootstrap current fraction shrinks due to inductive current penetration. This shrink is prevented and the CH size can be controlled by appropriate external current drive (CD). The CH plasma is found to respond autonomically to external CD.

Journal Articles

A Review of internal transport barrier physics for steady-state operation of tokamaks

Connor, J. W.*; Fukuda, Takeshi*; Garbet, X.*; Gormezano, C.*; Mukhovatov, V.*; Wakatani, Masahiro*; ITB Database Group; ITPA Topical Group on Transport and Internal Barrier Physics*

Nuclear Fusion, 44(4), p.R1 - R49, 2004/04

 Times Cited Count:253 Percentile:23.26(Physics, Fluids & Plasmas)

This paper first reviews the present state of theoretical and experimental knowledge regarding the formation and characteristics of ITBs in tokamaks. Specifically, the current status of theoretical modeling of ITBs is presented; then, an international ITB database based on experimental information extracted from some nine tokamaks is described and used to draw some general conclusions concerning the necessary conditions for ITBs to appear, comparing these with the theoretical models. The experimental situation regarding the steady-state, or at least quasi-steady-state, operation of tokamaks is reviewed and finally the issues and prospects for achieving such operational modes in ITER are discussed.

Journal Articles

Instantaneous correlation between ELM-like MHD activity and abrupt non-local reduction of transport at internal transport barrier formation in JT-60U high-$$beta$$$$_{p}$$ plasmas

Neudatchin, S.*; Takizuka, Tomonori; Hayashi, Nobuhiko; Isayama, Akihiko; Shirai, Hiroshi; Fujita, Takaaki; Kamada, Yutaka; Koide, Yoshihiko; Ito, Kimitaka*; Miura, Yukitoshi

Purazuma, Kaku Yugo Gakkai-Shi, 79(12), p.1218 - 1220, 2003/12

New type of edge-core instantaneous interplay in JT-60U high-$$beta$$$$_{p}$$ plasmas is found. Abrupt in time and wide in space reduction of electron heat flux in the core (called ITB-event) is correlated in ms timescale with the start of an ELM. This result gives a hint of the control to form the ITB immedeately and non-locally by inducing the ELM-like MHD activity.

Journal Articles

Prospect for "multiple-hierarchical complex plasma" where turbulent and laminar flow fluctuations are mixed

Kishimoto, Yasuaki; Idomura, Yasuhiro; Li, J.

Purazuma, Kaku Yugo Gakkai-Shi, 79(5), p.478 - 488, 2003/05

This is a collection of review article related to the "Multiple Time and Spatial Scale Plasma Simulation" of various fields including fundamental research area of self-organization, magnetic and laser fusion field, space and astrophysics field where a plasma plays an essential roles.

JAEA Reports

Review of JT-60U experimental results in 2000

JT-60 Team

JAERI-Review 2002-022, 149 Pages, 2002/11

JAERI-Review-2002-022.pdf:10.21MB

no abstracts in English

Journal Articles

Magnetohydrodynamic stability of improved confinement plasmas in JT-60U

Takeji, Satoru; Isayama, Akihiko; Ozeki, Takahisa; Tokuda, Shinji; Ishii, Yasutomo; Oikawa, Toshihiro; Ishida, Shinichi; Kamada, Yutaka; Neyatani, Yuzuru; Yoshino, Ryuji; et al.

Fusion Science and Technology (JT-60 Special Issue), 42(2-3), p.278 - 297, 2002/09

 Times Cited Count:7 Percentile:90.91(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Evolution of lower hybrid driven current during the formation of an internal transport barrier

Naito, Osamu; Cui, Z.*; Ide, Shunsuke; Suzuki, Takahiro; Oikawa, Toshihiro; Seki, Masami; Hatae, Takaki; Fujita, Takaaki; Kondoh, Takashi; Shirai, Hiroshi; et al.

Physical Review Letters, 89(6), p.065001_1 - 065001_4, 2002/08

 Times Cited Count:9 Percentile:45.92(Physics, Multidisciplinary)

Evolution of lower hybrid (LH) driven current profile was measured during the formation of internal transport barrier (ITB) in a reversed magnetic shear discharge. As the ITB developed, initially centrally peaked LH driven current profile gradually turned hollow and was sometimes accompanied by an off-axis peak in electron temperature profile followed by a sawtooth-like instability localized to the ITB. These observations indicate the concentration of LH power deposition at the ITB and suggest the difficulty of current profile control by LH waves once the ITB is established.

Journal Articles

Research activities on Tokamaks in Japan; JT-60U, JFT-2M and TRIAM-1M

Ninomiya, Hiromasa; Kitsunezaki, Akio; Shimizu, Masatsugu; Kuriyama, Masaaki; JT-60 Team; Kimura, Haruyuki; Kawashima, Hisato; Tsuzuki, Kazuhiro; Sato, Masayasu; Isei, Nobuaki; et al.

Fusion Science and Technology, 42(1), p.7 - 31, 2002/07

 Times Cited Count:12 Percentile:75.76(Nuclear Science & Technology)

In order to establish scientific basis for the sustainment of highly integrated performance required in the advanced steady-state operation, JT-60U has been optimizing the discharge control scenarios of improved confinement plasmas and expanding the operation regions. Promising results toward the steady-state tokamak were obtained. The detail of such results is reported. JFT-2M has performed advanced and basic research for the development of high performance tokamak plasma as well as the structural material for a fusion reactor. The toroidal ripple reduction with ferritic steel plates outside the vacuum vessel was successfully demonstrated. No adverse effects were observed in the pre-testing on compatibility between ferritic steel plates, covering ~20% of the inside wall of the vacuum vessel, and plasma. The results of TRIAM-1M is also reported.

Journal Articles

Heterodyne O-mode reflectometer on the JT-60U tokamak

Oyama, Naoyuki; Shinohara, Koji

Review of Scientific Instruments, 73(3), p.1169 - 1176, 2002/03

 Times Cited Count:19 Percentile:31.04(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Overview of JT-60U results toward high integrated performance in reactor-relevant regime

Hatae, Takaki; JT-60 Team

Proceedings of 6th Japan-Australia Workshop on Plasma Diagnostics (CD-ROM), 13 Pages, 2002/00

The main purpose of JT-60U project is to make contribution to establishment of scientific basis of ITER and the demo tokamak reactor. Our ultimate goal is to achieve and sustain high integrated performance, namely high beta, high confinement, high bootstrap current fraction, full non-inductive current drive and heat/particle control, in a reactor-relevant regime. Toward this goal, we have developed weak magnetic shear ("high $$beta_{p}$$ mode") and reversed magnetic shear plasmas. In both regimes, the internal transport barrier (ITB) and the edge pedestal are obtained simultaneously. As a large-sized tokamak equipped with a variety of devices for heating, current drive and profile control, JT-60U has high ability to approach the conditions required in reactors (ITER or demo): low values of normalized Larmor radius and collisionality, high toroidal field, high temperature with Te$$>sim$$Ti, small central fueling, small ELM activities, etc. This paper reviews recent JT-60U results with the emphasis on the projection to the reactor-relevant regime.

JAEA Reports

Review of JT-60U experimental results from February to October, 1999

JT-60 Team

JAERI-Review 2000-035, 164 Pages, 2001/02

JAERI-Review-2000-035.pdf:10.14MB

no abstracts in English

Journal Articles

Comparison of edge pedestal parameters for JT-60U and DIII-D H-mode plasmas

Hatae, Takaki; Osborne, T. H.*; Kamada, Yutaka; Groebner, R. J.*; Takizuka, Tomonori; Fukuda, Takeshi; Lao, L. L.*

Plasma Physics and Controlled Fusion, 42(suppl.5A), p.A283 - A288, 2000/05

 Times Cited Count:8 Percentile:71.47(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

ITER Physics R&D Expert Group report

Wakatani, Masahiro*; Fukuda, Takeshi; Toi, Kazuo*; Takizuka, Tomonori; Miura, Yukitoshi; Ogawa, Yuichi*; Kamada, Yutaka; Oyabu, Nobuyoshi*; Hatae, Takaki

Purazuma, Kaku Yugo Gakkai-Shi, 76(2), p.175 - 177, 2000/02

no abstracts in English

Journal Articles

Study of internal transport barriers by comparison of reversed shear and high-$$beta$$$$_{p}$$ discharges in JT-60U

Koide, Yoshihiko; Mori, Masahiro; Fujita, Takaaki; Shirai, Hiroshi; Hatae, Takaki; Takizuka, Tomonori; Kimura, Haruyuki; Oikawa, Toshihiro; Isei, Nobuaki; Isayama, Akihiko; et al.

Plasma Physics and Controlled Fusion, 40(5), p.641 - 645, 1998/00

 Times Cited Count:25 Percentile:35.88(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Ideal magnetohydrodynamic instabilities with low toroidal mode numbers localized near an internal transport barrier in high-$$beta$$p mode plasmas in the Japan Atomic Energy Research Institute Tokamak-60 upgrade

Takeji, Satoru; Kamada, Yutaka; Ozeki, Takahisa; Ishida, Shinichi; Takizuka, Tomonori; Neyatani, Yuzuru; Tokuda, Shinji

Physics of Plasmas, 4(12), p.4283 - 4291, 1997/12

 Times Cited Count:16 Percentile:47.68(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Kinetic ballooning modes at the tokamak transport barrier with negative magnetic shear

Yamagiwa, Mitsuru; *; M.Elia*

Physics of Plasmas, 4(11), p.4031 - 4034, 1997/11

 Times Cited Count:2 Percentile:90.53(Physics, Fluids & Plasmas)

no abstracts in English

26 (Records 1-20 displayed on this page)