The National Spherical Torus Experiment (NSTX) research programme and progress towards high beta, long pulse operating scenarios.
- Princeton University, Princeton, NJ
- Oak Ridge National Laboratory, Oak Ridge, TN
- Columbia University, New York, NY
- University of Washington, Seattle, WA,
- University of California, Los Angeles, CA
- CEA Cadarache, France
- Los Alamos National Laboratory, Los Alamos, NM
- University of California, San Diego, CA
- University of New Mexico, Albuquerque, NM
- Johns Hopkins University, Baltimore, MD
- University of Washington, Seattle, WA
- University of California, Davis, CA
A major research goal of the national spherical torus experiment is establishing long-pulse, high beta, high confinement operation and its physics basis. This research has been enabled by facility capabilities developed during 2001 and 2002, including neutral beam (up to 7 MW) and high harmonic fast wave (HHFW) heating (up to 6 MW), toroidal fields up to 6 kG, plasma currents up to 1.5 MA, flexible shape control, and wall preparation techniques. These capabilities have enabled the generation of plasmas with {beta}{sub T} {triple_bond} <p>/(B{sub T0}{sup 2}/2{mu}{sub 0}) of up to 35%. Normalized beta values often exceed the no-wall limit, and studies suggest that passive wall mode stabilization enables this for H mode plasmas with broad pressure profiles. The viability of long, high bootstrap current fraction operations has been established for ELMing H mode plasmas with toroidal beta values in excess of 15% and sustained for several current relaxation times. Improvements in wall conditioning and fueling are likely contributing to a reduction in H mode power thresholds. Electron thermal conduction is the dominant thermal loss channel in auxiliary heated plasmas examined thus far. HHFW effectively heats electrons, and its acceleration of fast beam ions has been observed. Evidence for HHFW current drive is obtained by comparison of the loop voltage evolution in plasmas with matched density and temperature profiles but varying phases of launched HHFW waves. Studies of emissions from electron Bernstein waves indicate a density scale length dependence of their transmission across the upper hybrid resonance near the plasma edge that is consistent with theoretical predictions. A peak heat flux to the divertor targets of 10 MW m{sup -2} has been measured in the H mode, with large asymmetries being observed in the power deposition between the inner and outer strike points. Non-inductive plasma startup studies have focused on coaxial helicity injection. With this technique, toroidal currents up to 400 kA have been driven, and studies to assess flux closure and coupling to other current drive techniques have begun.
- Research Organization:
- Sandia National Laboratories (SNL), Albuquerque, NM, and Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 960271
- Report Number(s):
- SAND2004-3119J; TRN: US0904360
- Journal Information:
- Proposed for publication in Nuclear Fusion., Vol. 43, Issue 12
- Country of Publication:
- United States
- Language:
- English
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The national spherical torus experiment (NSTX) research programme and progress towards high beta, long pulse operating scenarios
The national spherical torus experiment (NSTX) research programme and progress towards high beta, long pulse operating scenarios