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

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 withmore » 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.« less
Authors:
; ; ; ; ; ; ; ;  [1] ;  [2] ; ; ; ; ;  [3] ; ;  [4] ; ;  [5] ;  [6] more »; « less
  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)
Publication Date:
OSTI Identifier:
22496187
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1689; Journal 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)
Country of Publication:
United States
Language:
English
Subject:
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