Steady-state improved confinement studies in the JT-60U tokamak

Journal Article · Thu Jun 01 04:00:00 EDT 1995 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.871486· OSTI ID:165298

Fukuda, T ^[1]

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1. Japan Atomic Energy Research Institute, Naka-machi, Naka-gun, Ibaraki-ken 311-01 (Japan)

As a result of dynamic control of the heat deposition and current profile, notably a large fusion product 4{times}10{sup 20} m{sup {minus}3} s keV (equivalent {ital Q}{sub DT}=0.25) was sustained for 1.5 s in the high-confinement mode (H-mode) discharge accompanied with the edge localized modes (ELM), while the highest performance achieved transiently was 1.2{times}10{sup 21} m{sup {minus}3} s keV (equivalent {ital Q}{sub DT}=0.46). A doubly formed transport barrier at the {ital q}=3 surface and near the edge is essential for the improvement in confinement. It has also been found that the active shear formation in the toroidal flow velocity, as well as the magnetic shear, can increase the critical edge pressure at the onset of ELMs, which constrain the maximum fusion performance. Further extension to the high-{beta}{sub {ital N}} (={l_angle}{beta}{sub {ital t}}{r_angle}{ital a}{sub {ital p}}{ital B}{sub {ital T}}/{ital I}{sub {ital p}}) regime yielded the values of {beta}{sub {ital N}}=2.9, {beta}{sub {ital p}}=2.6 and the H-factor (={tau}{sub {ital E}}/{tau}{sub {ital E}}{sup ITER-89P}) of 2.5 for 0.7 s under the full current-drive condition. In these high-{beta}{sub {ital N}} discharges, the bootstrap component was 74% of the total plasma current before the beam injection, while the neutral beam current drive (NBCD) fraction was 37%. It is stressed that effective current drive in the central region, which can sustain the peaked current profile against the bootstrap component, is indispensable for the efficient steady-state operation. Major results from the confinement physics studies, such as the characteristics of the primary barrier and the turbulence transport across the secondary barrier, are also addressed in this paper. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

• OSTI ID: 165298
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 6 Vol. 2; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
CURRENT-DRIVE HEATING
DIVERTORS
FUSION YIELD
HIGH-BETA PLASMA
JT-60 TOKAMAK
PLASMA CONFINEMENT
THERMONUCLEAR DEVICES
TURBULENCE