Recent Fast Wave Coupling and Heating Studies on NSTX, with Possible Implications for ITER
- Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States)
- CompX, Del Mar, CA 92014 (United States)
- Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)
- Johns Hopkins University, Baltimore, MD 21218 (United States)
The goal of the high harmonic fast wave (HHFW) research on NSTX is to maximize the coupling of RF power to the core of the plasma by minimizing the coupling of RF power to edge loss processes. HHFW core plasma heating efficiency in helium and deuterium L-mode discharges is found to improve markedly on NSTX when the density 2 cm in front of the antenna is reduced below that for the onset of perpendicular wave propagation (n{sub onset}{proportional_to}B*k{sub parallel}{sup 2}/{omega}). In NSTX, the observed RF power losses in the plasma edge are driven in the vicinity of the antenna as opposed to resulting from multi-pass edge damping. PDI surface losses through ion-electron collisions are estimated to be significant. Recent spectroscopic measurements suggest that additional PDI losses could be caused by the loss of energetic edge ions on direct loss orbits and perhaps result in the observed clamping of the edge rotation. Initial deuterium H-mode heating studies reveal that core heating is degraded at lower k{sub {phi}}(-8 m{sup -1} relative to 13 m{sup -1}) as for the L-mode case at elevated edge density. Fast visible camera images clearly indicate that a major edge loss process is occurring from the plasma scrape off layer (SOL) in the vicinity of the antenna and along the magnetic field lines to the lower outer divertor plate. Large type I ELMs, which are observed at both k{sub {phi}} values, appear after antenna arcs caused by precursor blobs, low level ELMs, or dust. For large ELMs without arcs, the source reflection coefficients rise on a 0.1 ms time scale, which indicates that the time derivative of the reflection coefficient can be used to discriminate between arcs and ELMs.
- OSTI ID:
- 21335684
- Journal Information:
- AIP Conference Proceedings, Vol. 1187, Issue 1; Conference: 18. topical conference on radio frequency power in plasmas, Gent (Belgium), 24-26 Jun 2009; Other Information: DOI: 10.1063/1.3273706; (c) 2009 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
DAMPING
DEUTERIUM
DIVERTORS
EDGE LOCALIZED MODES
ELECTRON-ION COLLISIONS
HELIUM
H-MODE PLASMA CONFINEMENT
IONS
ITER TOKAMAK
L-MODE PLASMA CONFINEMENT
MAGNETIC FIELDS
NSTX DEVICE
PLASMA
PLASMA DENSITY
PLASMA HEATING
PLASMA SCRAPE-OFF LAYER
PLASMA WAVES
WAVE PROPAGATION