Demonstration of high-performance negative central magnetic shear discharges in the DIII-D tokamak

Journal Article · Wed May 01 04:00:00 EDT 1996 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.871994· OSTI ID:283418

Rice, B W; Burrell, K H; Lao, L L; Navratil, G; Stallard, B W; Strait, E J; Taylor, T S; Austin, M E; Casper, T A; Chu, M S; Forest, C B; Gohil, P; Groebner, R J; Heidbrink, W W; Hyatt, A W; Ikezi, H; La Haye, R J; Lazarus, E A; Lin-Liu, Y R; Mauel, M E ; Meyer, W H; Rettig, C L; Schissel, D P; John, H E; Taylor, P L; Turnbull, A D ^[1]

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1. General Atomics, P.O. Box 85608, San Diego, California 92186-9784 (United States)

Reliable operation of discharges with negative central magnetic shear has led to significant increases in plasma performance and reactivity in both low confinement, L-mode, and high confinement, H-mode, regimes in the DIII-D tokamak [{ital Plasma} {ital Physics} {ital and} {ital Controlled} {ital Nuclear} {ital Fusion} {ital Research} 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. 1, p. 159]. Using neutral beam injection early in the initial current ramp, a large range of negative shear discharges have been produced with durations lasting up to 3.2 s. The total noninductive current (beam plus bootstrap) ranges from 50{percent} to 80{percent} in these discharges. In the region of shear reversal, significant peaking of the toroidal rotation [{ital f}{sub {phi}}(0){approximately}30{endash}60 kHz] and ion temperature [{ital T}{sub {ital i}}(0){approximately}15{endash}22 keV] profiles are observed. In high-power discharges with an L-mode edge, peaked density profiles are also observed. Confinement enhancement factors up to {ital H}{equivalent_to}{tau}{sub {ital E}}/{tau}{sub ITER-89P}{approximately}2.5 with an L-mode edge, and {ital H}{approximately}3.3 in an edge localized mode (ELM)-free H mode, are obtained. Transport analysis shows both ion thermal diffusivity and particle diffusivity to be near or below standard neoclassical values in the core. Large pressure peaking in the L mode leads to high disruptivity with {beta}{sub {ital N}}{equivalent_to}{beta}{sub {ital T}}/({ital I}/{ital aB}){le}2.3, while broader pressure profiles in the H mode gives low disruptivity with {beta}{sub {ital N}}{le}4.2. {copyright} {ital 1996 American Institute of Physics.}

• Research Organization: General Atomics
• DOE Contract Number: AC03-89ER51114; AC05-84OR21400; FG02-89ER53297; FG05-88ER53266; W-7405-ENG-48
• OSTI ID: 283418
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 5 Vol. 3; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BOOTSTRAP CURRENT
DOUBLET-3 DEVICE
H-MODE PLASMA CONFINEMENT
HIGH-BETA PLASMA
PERFORMANCE
PLASMA HEATING
TOKAMAK DEVICES