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Title: Fast-ion transport in qmin >2, high-β steady state scenarios on DIII-D

Results from experiments on DIII-D aimed at developing high β steady-state operating scenarios with high-qmin 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 megawatts of neutral beam heating power is applied with the intent of maximizing βN and the noninductive current drive. However, in scenarios with qmin > 2 that target the typical range of q95 = 5-7 used in next-step steady-state reactor models, Alfven 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 βN. In contrast, similar plasmas except with qmin just above 1 have approximately classical fast-ion transport. Experiments that take qmin > 3 plasmas to higher βp with q95 = 11-12 for testing long pulse operation exhibit regimes of better than expected thermal confinement. Compared to the standard high- qmin scenario the high βp cases have shorter slowing-down time and lower Lambda βfast, and this reduces the drive for Alfvénic modes, yielding nearly classical fast-ion transport, high values of normalized confinement, βN, and noninductive current fraction. In conclusion, these results suggest DIII-D might obtain bettermore » performance in lower-q95, high-qmin plasmas using broader neutral beam heating profiles and increased direct electron heating power to lower the drive for Alfven eigenmodes.« less
 [1] ;  [2] ;  [3] ;  [3] ;  [3] ;  [4] ;  [5] ;  [4] ;  [4] ;  [3] ;  [2] ;  [6] ;  [6] ;  [3] ;  [7] ;  [3] ;  [3] ;  [4]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. Univ. of California, Irvine, CA (United States)
  3. General Atomics, San Diego, CA (United States)
  4. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  5. Chinese Academy of Sciences (CAS), Beijing (China)
  6. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  7. Columbia Univ., New York, NY (United States)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 22; Journal ID: ISSN 1070-664X
American Institute of Physics (AIP)
Research Org:
General Atomics, San Diego, CA (United States)
Sponsoring Org:
USDOE Office of Nuclear Energy (NE)
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1329394