Fast-ion transport in q{sub min}>2, high-β steady-state scenarios on DIII-D
- Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)
- Department of Physics and Astronomy, University of California Irvine, Irvine, California 92697 (United States)
- General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)
- Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 05843 (United States)
- Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui 230031 (China)
- Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831 (United States)
- Columbia University, 2960 Broadway, New York, New York 10027 (United States)
Results from experiments on DIII-D [J. L. Luxon, Fusion Sci. Technol. 48, 828 (2005)] aimed at developing high β steady-state operating scenarios with high-q{sub min} confirm that fast-ion transport is a critical issue for advanced tokamak development using neutral beam injection current drive. In DIII-D, greater than 11 MW of neutral beam heating power is applied with the intent of maximizing β{sub N} and the noninductive current drive. However, in scenarios with q{sub min}>2 that target the typical range of q{sub 95}= 5–7 used in next-step steady-state reactor models, Alfvén eigenmodes cause greater fast-ion transport than classical models predict. This enhanced transport reduces the absorbed neutral beam heating power and current drive and limits the achievable β{sub N}. In contrast, similar plasmas except with q{sub min} just above 1 have approximately classical fast-ion transport. Experiments that take q{sub min}>3 plasmas to higher β{sub P} with q{sub 95}= 11–12 for testing long pulse operation exhibit regimes of better than expected thermal confinement. Compared to the standard high-q{sub min} scenario, the high β{sub P} cases have shorter slowing-down time and lower ∇β{sub fast}, and this reduces the drive for Alfvénic modes, yielding nearly classical fast-ion transport, high values of normalized confinement, β{sub N}, and noninductive current fraction. These results suggest DIII-D might obtain better performance in lower-q{sub 95}, high-q{sub min} plasmas using broader neutral beam heating profiles and increased direct electron heating power to lower the drive for Alfvén eigenmodes.
- OSTI ID:
- 22410381
- Journal Information:
- Physics of Plasmas, Vol. 22, Issue 5; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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