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Title: Fast-ion transport in q{sub min}>2, high-β steady-state scenarios on DIII-D

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{submore » 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.« less
Authors:
 [1] ; ;  [2] ; ; ; ; ; ;  [3] ; ; ; ;  [4] ; ;  [5] ; ;  [6] ;  [7]
  1. Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)
  2. Department of Physics and Astronomy, University of California Irvine, Irvine, California 92697 (United States)
  3. General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)
  4. Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 05843 (United States)
  5. Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui 230031 (China)
  6. Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831 (United States)
  7. Columbia University, 2960 Broadway, New York, New York 10027 (United States)
Publication Date:
OSTI Identifier:
22410381
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 5; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; BEAM INJECTION; CHARGED-PARTICLE TRANSPORT; DOUBLET-3 DEVICE; ELECTRONS; IONS; PARTICLE BEAMS; PLASMA; PLASMA CONFINEMENT; STEADY-STATE CONDITIONS