Effect of the scrape-off layer in AORSA full wave simulations of fast wave minority, mid/high harmonic, and helicon heating regimes

Journal Article · Thu Dec 10 00:00:00 EST 2015 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.4936475· OSTI ID:22496187

Gerhardt, S.; Hosea, J. C.; LeBlanc, B.; Perkins, R. J.; Phillips, C. K.; Taylor, G.; Valeo, E. J.; Wilson, J. R. ^[1]; Jaeger, E. F. ^[2]; Lau, C.; Blazevski, D.; Green, D. L.; Berry, L.; Ryan, P. M. ^[3]; Bonoli, P. T.; Wright, J. C. ^[4]; Pinsker, R. I.; Prater, R. ^[5]; Qin, C. M. ^[6]; others, and

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1. Princeton Plasma Physics Laboratory, Princeton, NJ 08543 (United States)
2. XCEL Engineering Inc., Oak Ridge, TN 37830 (United States)
3. Oak Ridge National Laboratory, Oak Ridge, TN 37831-6169 (United States)
4. MIT Plasma Science and Fusion Center, Cambridge, MA 02139 (United States)
5. General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States)
6. Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China)

Several experiments on different machines and in different fast wave (FW) heating regimes, such as hydrogen minority heating and high harmonic fast waves, have found strong interactions between radio-frequency (RF) waves and the scrape-off layer (SOL) region. This paper examines the propagation and the power loss in the SOL by using the full wave code AORSA, in which the edge plasma beyond the last closed flux surface (LCFS) is included in the solution domain and a collisional damping parameter is used as a proxy to represent the real, and most likely nonlinear, damping processes. 3D AORSA results for the National Spherical Torus eXperiment (NSTX), where a full antenna spectrum is reconstructed, are shown, confirming the same behavior found for a single toroidal mode results in Bertelli et al, Nucl. Fusion, 54 083004, 2014, namely, a strong transition to higher SOL power losses (driven by the RF field) when the FW cut-off is moved away from in front of the antenna by increasing the edge density. Additionally, full wave simulations have been extended to “conventional” tokamaks with higher aspect ratios, such as the DIII-D, Alcator C-Mod, and EAST devices. DIII-D results show similar behavior found in NSTX and NSTX-U, consistent with previous DIII-D experimental observations. In contrast, a different behavior has been found for Alcator C-Mod and EAST, which operate in the minority heating regime unlike NSTX/NSTX-U and DIII-D, which operate in the mid/high harmonic regime. A substantial discussion of some of the main aspects, such as (i) the pitch angle of the magnetic field; (ii) minority heating vs. mid/high harmonic regimes is presented showing the different behavior of the RF field in the SOL region for NSTX-U scenarios with different plasma current. Finally, the preliminary results of the impact of the SOL region on the evaluation of the helicon current drive efficiency in DIII-D is presented for the first time and briefly compared with the different regimes mentioned above.

• OSTI ID: 22496187
• Journal Information: AIP Conference Proceedings, Vol. 1689, Issue 1; Conference: 21. topical conference on radio frequency power in plasmas, Lake Arrowhead, CA (United States), 27-29 Apr 2015; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ALCATOR DEVICE
ANTENNAS
ASPECT RATIO
COMPARATIVE EVALUATIONS
DAMPING
DENSITY
DOUBLET-3 DEVICE
ELECTRIC CURRENTS
HEATING
HYDROGEN
MAGNETIC FIELDS
MAGNETIC SURFACES
NONLINEAR PROBLEMS
NSTX DEVICE
PLASMA
PLASMA SCRAPE-OFF LAYER
POWER LOSSES
RADIOWAVE RADIATION
SIMULATION
STRONG INTERACTIONS