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

Conference · Mon Jan 01 04:00:00 EST 1996

OSTI ID:390416

Rice, B W ^[1]; Burrell, K H; Lao, L L ^[2]

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1. Lawrence Livermore National Lab., CA (United States)
2. General Atomics, San Diego, CA (United States); and others

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. 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 non- inductive current (beam plus bootstrap) ranges from 50% to 80% in these discharges. In the region of shear reversal, significant peaking of the toroidal rotation [f{sub {phi}} {approx} 30-60 kHz] and ion temperature [T{sub i}(0) {approx} 15-22 keV] profiles are observed. In high power discharges with an L-mode edge, peaked density profiles are also observed. Confinement enhancement factors up to H {equivalent_to} {tau}{sub E}/{tau}{sub ITER-89P} {approx} 2.5 with an L-mode edge, and H {approx} 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 L- mode leads to high disruptivity with {Beta}{sub N} {equivalent_to} {Beta}{sub T}/(I/aB) {<=} 2.3, while broader pressure profiles in H- mode gives low disruptivity with {Beta}{sub N} {<=} 4.2.

• Research Organization: General Atomics, San Diego, CA (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC03-89ER51114; AC05-96OR22464; FG02-89ER53297; FG05-88ER53266; W-7405-ENG-48
• OSTI ID: 390416
• Report Number(s): GA--A22257; CONF-951182--15; ON: DE96015244
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
DOUBLET-3 DEVICE
EDGE LOCALIZED MODES
H-MODE PLASMA CONFINEMENT
HIGH-BETA PLASMA
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
NEUTRAL ATOM BEAM INJECTION
PLASMA
PLASMA MACROINSTABILITIES
SHEAR