High-beta steady-state research with integrated modeling in the JT-60 Upgrade
Abstract
Improvement of high-beta performance and its long sustainment was obtained with ferritic steel tiles in the JT-60 Upgrade (JT-60U) [T. Fujita et al., Phys. Plasmas 50, 104 (2005)], which were installed inside the vacuum vessel to reduce fast ion loss by decreasing the toroidal field ripple. When a separation between the plasma surface and the wall was small, high-beta plasmas reached the ideal wall stability limit, i.e., the ideal magnetohydrodynamics stability limit with the wall stabilization. A small rotation velocity of 0.3% of the Alfven velocity was found to be effective for suppressing the resistive wall mode. Sustainment of the high normalized beta value of {beta}{sub N}=2.3 has been extended to 28.6 s ({approx}15 times the current diffusion time) by improvement of the confinement and increase in the net heating power. Based on the research in JT-60U experiments and first-principle simulations, integrated models of core, edge-pedestal, and scrape-off-layer (SOL) divertors were developed, and they clarified complex features of reactor-relevant plasmas. The integrated core plasma model indicated that the small amount of electron cyclotron (EC) current density of about half the bootstrap current density could effectively stabilize the neoclassical tearing mode by the localized EC current accurately aligned to the magneticmore »
- Authors:
- Fusion Research and Development Directorate, Japan Atomic Energy Agency, Naka, Ibaraki 311-0193 (Japan)
- Publication Date:
- OSTI Identifier:
- 20975052
- Resource Type:
- Journal Article
- Resource Relation:
- Journal Name: Physics of Plasmas; Journal Volume: 14; Journal Issue: 5; Other Information: DOI: 10.1063/1.2718518; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; BOOTSTRAP CURRENT; CYCLOTRONS; EDGE LOCALIZED MODES; ELECTRONS; ENERGY LOSSES; FERRITIC STEELS; HIGH-BETA PLASMA; JT-60 TOKAMAK; JT-60U TOKAMAK; MAGNETOHYDRODYNAMICS; NEOCLASSICAL TRANSPORT THEORY; PLASMA SCRAPE-OFF LAYER; SIMULATION; TEARING INSTABILITY; WALLS
Citation Formats
Ozeki, T. High-beta steady-state research with integrated modeling in the JT-60 Upgrade. United States: N. p., 2007.
Web. doi:10.1063/1.2718518.
Ozeki, T. High-beta steady-state research with integrated modeling in the JT-60 Upgrade. United States. doi:10.1063/1.2718518.
Ozeki, T. Tue .
"High-beta steady-state research with integrated modeling in the JT-60 Upgrade". United States.
doi:10.1063/1.2718518.
@article{osti_20975052,
title = {High-beta steady-state research with integrated modeling in the JT-60 Upgrade},
author = {Ozeki, T.},
abstractNote = {Improvement of high-beta performance and its long sustainment was obtained with ferritic steel tiles in the JT-60 Upgrade (JT-60U) [T. Fujita et al., Phys. Plasmas 50, 104 (2005)], which were installed inside the vacuum vessel to reduce fast ion loss by decreasing the toroidal field ripple. When a separation between the plasma surface and the wall was small, high-beta plasmas reached the ideal wall stability limit, i.e., the ideal magnetohydrodynamics stability limit with the wall stabilization. A small rotation velocity of 0.3% of the Alfven velocity was found to be effective for suppressing the resistive wall mode. Sustainment of the high normalized beta value of {beta}{sub N}=2.3 has been extended to 28.6 s ({approx}15 times the current diffusion time) by improvement of the confinement and increase in the net heating power. Based on the research in JT-60U experiments and first-principle simulations, integrated models of core, edge-pedestal, and scrape-off-layer (SOL) divertors were developed, and they clarified complex features of reactor-relevant plasmas. The integrated core plasma model indicated that the small amount of electron cyclotron (EC) current density of about half the bootstrap current density could effectively stabilize the neoclassical tearing mode by the localized EC current accurately aligned to the magnetic island center. The integrated edge-pedestal model clarified that the collisionality dependence of energy loss due to the edge-localized mode was caused by the change in the width of the unstable mode and the SOL transport. The integrated SOL-divertor model clarified the effect of the exhaust slot on the pumping efficiency and the cause of enhanced radiation near the X-point multifaceted asymmetric radiation from edge. Success in these consistent analyses using the integrated code indicates that it is an effective means to investigate complex plasmas and to control the integrated performance.},
doi = {10.1063/1.2718518},
journal = {Physics of Plasmas},
number = 5,
volume = 14,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
-
Researches on advanced tokamak (AT) have progressed with integrated modeling in JT-60 Upgrade [N. Oyama et al., Nucl. Fusion 49, 104007 (2009)]. Based on JT-60U experimental analyses and first principle simulations, new models were developed and integrated into core, rotation, edge/pedestal, and scrape-off-layer (SOL)/divertor codes. The integrated models clarified complex and autonomous features in AT. An integrated core model was implemented to take account of an anomalous radial transport of alpha particles caused by Alfven eigenmodes. It showed the reduction in the fusion gain by the anomalous radial transport and further escape of alpha particles. Integrated rotation model showed mechanismsmore »
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Steady-state sustainment of high-{beta} plasmas through stability control in Japan Atomic Energy Research Institute Tokamak-60 Upgrade
Recent results from steady-state sustainment of high-{beta} plasma experiments in the Japan Atomic Energy Research Institute Tokamak-60 Upgrade (JT-60U) tokamak [A. Kitsunezaki et al., Fusion Sci. Technol. 42, 179 (2002)] are described. Extension of discharge duration to 65 s (formerly 15 s) has enabled physics research with long time scale. In long-duration high-{beta} research, the normalized beta {beta}{sub N}=2.5, which is comparable to that in the steady-state operation in International Thermonuclear Experimental Reactor (ITER) [R. Aymar, P. Barabaschi, and Y. Shimomura, Plasma Phys. Controlled Fusion 44, 519 (2002)], has been sustained for about 15 s with confinement enhancement factor H{submore » -
Recent results from high performance and steady-state researches in the Japan Atomic Energy Research Institute Tokamak-60 Upgrade
High {ital I}{sub {ital P}} hot ion high confinement (H) mode at {ital I}{sub {ital P}} up to 4.5 MA has been exploited. Sawtooth stabilization by ion cyclotron range of frequencies (ICRF) heating is effective to improve performance in this regime. The performance is limited by the onset of giant edge localized modes (ELMs). It was found that the edge pressure gradient at the onset of ELMs can be increased with increasing triangularity {delta} up to 0.4 at {ital I}{sub {ital P}}{lt}1.2 MA. The normalized beta ({beta}{sub {ital N}}) value at the ELM onset also increases from {approximately}1 to {approximately}2.8more » -
Progress in confinement and stability with plasma shape and profile control for steady-state operation in the Japan Atomic Energy Research Institute Tokamak-60 Upgrade
This paper describes the latest achievements of the Japan Atomic Energy Research Institute Tokamak-60 Upgrade (JT-60U) [H. Kimura and the JT-60 Team, Phys. Plasmas {bold 3}, 1943 (1996)] for the establishment of the physics and technology basis for steady-state, fully noninductive current-drive plasmas with high fusion performance. Recent results are highlighted by (1) high performance reversed-magnetic-shear discharges [an idealized equivalent Q{sub DT} of 1.05, a confinement-enhancement factor (H factor) of 3.23, and a normalized beta value ({beta}{sub N}) of 1.88 at I{sub p}=2.8MA/P{sub abs}=17MW]; the first observation of thermal transport barriers both for electrons and ions, (2) the first injectionmore » -
Advanced tokamak research on long time scales in JT-60 Upgrade
The duration of advanced tokamak plasma operation in JT-60 Upgrade (JT-60U) [A. Kitsunezaki et al., Fusion Sci. Technol. 42, 179 (2002)] has been extended on long time scales exceeding the current diffusion time ({tau}{sub R}) and close to the wall saturation time. A very high bootstrap current fraction (f{sub BS}) of 75% was maintained for 7.4 s (2.7{tau}{sub R}), while a normalized beta of 2.5 was maintained for 15.5 s ({approx}9.5{tau}{sub R}). The current profile reaches stationary conditions in {approx}{tau}{sub R} for the small f{sub BS} regime, while a longer time is required for the large f{sub BS} regime. Amore »