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Title: Recent progress toward an advanced spherical torus operating point in NSTX

Progress in the development of integrated advanced ST plasma scenarios in NSTX (Ono et al., 2000 Nucl. Fusion 40 557) is reported. Recent high-performance plasmas in NSTX following lithium coating of the plasma facing surfaces have achieved higher elongation and lower internal inductance than previously. Analysis of the thermal confinement in these lithiumized discharges shows a stronger plasma current and weaker toroidal field dependence than in previous ST confinement scaling studies; the ITER-98(y, 2) scaling expression describes these scenarios reasonably well. Analysis during periods free of MHD activity has shown that the reconstructed current profile can be understood as the sum of pressure driven, inductive and neutral beam driven currents, without requiring any anomalous fast-ion transport. Non-inductive fractions of 65–70%, and βP > 2, have been achieved at lower plasma current. Some of these low-inductance discharges have a significantly reduced no-wall βN limit, and often have βN at or near the with-wall limit. Coupled m/n = 1/1 + 2/1 kink/tearing modes can limit the sustained β values when rapidly growing ideal modes are avoided. A βN controller has been commissioned and utilized in sustaining high-performance plasmas. 'Snowflake' divertors compatible with high-performance plasmas have been developed. Scenarios with significantly larger aspectmore » ratios have also been developed, in support of next-step ST devices. Furthermore, these NSTX plasmas have many characteristics required for next-step ST devices.« less
Authors:
;  [1] ;  [1] ;  [2] ;  [1] ;  [3] ;  [4] ;  [1] ;  [1] ;  [3] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [5]
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Columbia Univ., New York, NY (United States)
  4. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  5. Nova Photonics, Princeton, NJ (United States)
Publication Date:
OSTI Identifier:
1266680
Report Number(s):
LLNL-JRNL--465266
Journal ID: ISSN 0029-5515
Grant/Contract Number:
AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 51; Journal Issue: 7; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Research Org:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION NSTX; spherical torus; MHD; plasma confinement