Accurate equilibrium reconstruction and detailed stability analysis of a strongly shaped, double‐null, βT=11% discharge shows that the plasma core is in the second stable regime to ideal ballooning modes. The equilibrium reconstruction using all the available data (coil currents, poloidal magnetic loops, motional Stark effect data, the kinetic pressure profile, the magnetic axis location, and the location of the two q=1 surfaces) shows a region of negative magnetic shear near the magnetic axis, an outer positive shear region, and a low shear region connecting the two. The inner negative shear region allows a large positive shear region near the boundary, even at low q (q95=2.6), permitting a large outer region pressure gradient to be first regime stable. The inner region is in the second stable regime, consistent with the observed axial beta [βT(0)=44%]. In the low shear region p′ vanishes, consistent with Mercier stability. This is one way to extend the ballooning limit in shaped plasmas while maintaining stability against external kinks. The n=1 analysis shows that the plasma is unstable to an ideal internal mode, consistent with the experimental observations of a saturated internal m/n=1/1 mode. The core plasma pressure, not being limited by ballooning stability, appears to be reaching a local equilibrium limit at the magnetic axis.
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November 1992
Research Article|
November 01 1992
An optimization of beta in the DIII‐D tokamak
E. A. Lazarus;
E. A. Lazarus
General Atomics, P.O. Box 85608, San Diego, California 92186‐9784
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L. L. Lao;
L. L. Lao
General Atomics, P.O. Box 85608, San Diego, California 92186‐9784
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T. H. Osborne;
T. H. Osborne
General Atomics, P.O. Box 85608, San Diego, California 92186‐9784
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T. S. Taylor;
T. S. Taylor
General Atomics, P.O. Box 85608, San Diego, California 92186‐9784
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A. D. Turnbull;
A. D. Turnbull
General Atomics, P.O. Box 85608, San Diego, California 92186‐9784
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M. S. Chu;
M. S. Chu
General Atomics, P.O. Box 85608, San Diego, California 92186‐9784
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A. G. Kellman;
A. G. Kellman
General Atomics, P.O. Box 85608, San Diego, California 92186‐9784
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E. J. Strait;
E. J. Strait
General Atomics, P.O. Box 85608, San Diego, California 92186‐9784
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J. R. Ferron;
J. R. Ferron
General Atomics, P.O. Box 85608, San Diego, California 92186‐9784
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R. J. Groebner;
R. J. Groebner
General Atomics, P.O. Box 85608, San Diego, California 92186‐9784
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W. W. Heidbrink;
W. W. Heidbrink
General Atomics, P.O. Box 85608, San Diego, California 92186‐9784
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T. Carlstrom;
T. Carlstrom
General Atomics, P.O. Box 85608, San Diego, California 92186‐9784
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F. J. Helton;
F. J. Helton
General Atomics, P.O. Box 85608, San Diego, California 92186‐9784
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C. L. Hsieh;
C. L. Hsieh
General Atomics, P.O. Box 85608, San Diego, California 92186‐9784
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S. Lippmann;
S. Lippmann
General Atomics, P.O. Box 85608, San Diego, California 92186‐9784
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D. Schissel;
D. Schissel
General Atomics, P.O. Box 85608, San Diego, California 92186‐9784
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R. Snider;
R. Snider
General Atomics, P.O. Box 85608, San Diego, California 92186‐9784
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D. Wroblewski
D. Wroblewski
General Atomics, P.O. Box 85608, San Diego, California 92186‐9784
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Phys. Fluids B 4, 3644–3662 (1992)
Article history
Received:
July 10 1991
Accepted:
July 23 1992
Citation
E. A. Lazarus, L. L. Lao, T. H. Osborne, T. S. Taylor, A. D. Turnbull, M. S. Chu, A. G. Kellman, E. J. Strait, J. R. Ferron, R. J. Groebner, W. W. Heidbrink, T. Carlstrom, F. J. Helton, C. L. Hsieh, S. Lippmann, D. Schissel, R. Snider, D. Wroblewski; An optimization of beta in the DIII‐D tokamak. Phys. Fluids B 1 November 1992; 4 (11): 3644–3662. https://doi.org/10.1063/1.860373
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