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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

Abstract

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];  [3];  [2];  [5];  [1];  [1];  [1];  [1];  [1];  [6];  [7];  [8];  [4];  [1];  [1];  [1];  [5] more »;  [8] « less
  1. Princeton Plasma Physics Laboratory (PPPL)
  2. XCEL Engineering Inc., Oak Ridge
  3. ORNL
  4. Oak Ridge National Laboratory (ORNL)
  5. Massachusetts Institute of Technology (MIT)
  6. General Atomics, San Diego
  7. General Atomics
  8. Chinese Academy of Sciences (CAS), Institute of Plasma Physics, Hefei
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1263865
DOE Contract Number:
AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Journal Volume: 1689; Conference: Radio Frequency Power in Plasma, Lakewood, CA, USA, 20150427, 20150429
Country of Publication:
United States
Language:
English

Citation Formats

Bertelli, Nicola, Jaeger, E. F., Lau, Cornwall H, Blazevski, Dan, Green, David L, Berry, Lee Alan, Bonoli, P. T., Gerhardt, S.P., Hosea, J. C., LeBlanc, B., Perkins, R. J., Phillips, Cynthia, Pinsker, R. I., Prater, R., Qin, C M, Ryan, P. M., Taylor, G., Valeo, E. J., Wilson, Randy, Wright, J., and Zhang, X J. Effect of the scrape-off layer in AORSA full wave simulations of fast wave minority, mid/high harmonic, and helicon heating regimes. United States: N. p., 2015. Web. doi:10.1063/1.4936475.
Bertelli, Nicola, Jaeger, E. F., Lau, Cornwall H, Blazevski, Dan, Green, David L, Berry, Lee Alan, Bonoli, P. T., Gerhardt, S.P., Hosea, J. C., LeBlanc, B., Perkins, R. J., Phillips, Cynthia, Pinsker, R. I., Prater, R., Qin, C M, Ryan, P. M., Taylor, G., Valeo, E. J., Wilson, Randy, Wright, J., & Zhang, X J. Effect of the scrape-off layer in AORSA full wave simulations of fast wave minority, mid/high harmonic, and helicon heating regimes. United States. doi:10.1063/1.4936475.
Bertelli, Nicola, Jaeger, E. F., Lau, Cornwall H, Blazevski, Dan, Green, David L, Berry, Lee Alan, Bonoli, P. T., Gerhardt, S.P., Hosea, J. C., LeBlanc, B., Perkins, R. J., Phillips, Cynthia, Pinsker, R. I., Prater, R., Qin, C M, Ryan, P. M., Taylor, G., Valeo, E. J., Wilson, Randy, Wright, J., and Zhang, X J. Thu . "Effect of the scrape-off layer in AORSA full wave simulations of fast wave minority, mid/high harmonic, and helicon heating regimes". United States. doi:10.1063/1.4936475.
@article{osti_1263865,
title = {Effect of the scrape-off layer in AORSA full wave simulations of fast wave minority, mid/high harmonic, and helicon heating regimes},
author = {Bertelli, Nicola and Jaeger, E. F. and Lau, Cornwall H and Blazevski, Dan and Green, David L and Berry, Lee Alan and Bonoli, P. T. and Gerhardt, S.P. and Hosea, J. C. and LeBlanc, B. and Perkins, R. J. and Phillips, Cynthia and Pinsker, R. I. and Prater, R. and Qin, C M and Ryan, P. M. and Taylor, G. and Valeo, E. J. and Wilson, Randy and Wright, J. and Zhang, X J},
abstractNote = {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.},
doi = {10.1063/1.4936475},
journal = {},
number = ,
volume = 1689,
place = {United States},
year = {Thu Jan 01 00:00:00 EST 2015},
month = {Thu Jan 01 00:00:00 EST 2015}
}

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