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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:26.58(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:43.77(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:259 Percentile:76.74(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.

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

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:53.59(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

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

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:63.39(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Effects of radial gradient of the Shafranov shift on the kinetic ballooning and drift-type modes in high-performance tokamaks

*; Yamagiwa, Mitsuru

Canadian Journal of Physics, 75(9), p.599 - 604, 1997/09

no abstracts in English

12 (Records 1-12 displayed on this page)
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