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Title: Direct X-B mode conversion for high-β national spherical torus experiment in nonlinear regime

Abstract

Electron Bernstein wave (EBW) can be effective for heating and driving currents in spherical tokamak plasmas. Power can be coupled to EBW via mode conversion of the extraordinary (X) mode wave. The most common and successful approach to study the conditions for optimized mode conversion to EBW was evaluated analytically and numerically using a cold plasma model and an approximate kinetic model. The major drawback in using radio frequency waves was the lack of continuous wave sources at very high frequencies (above the electron plasma frequency), which has been addressed. A future milestone is to approach high power regime, where the nonlinear effects become significant, exceeding the limits of validity for present linear theory. Therefore, one appropriate tool would be particle in cell (PIC) simulation. The PIC method retains most of the nonlinear physics without approximations. In this work, we study the direct X-B mode conversion process stages using PIC method for incident wave frequency f{sub 0} = 15 GHz, and maximum amplitude E{sub 0} = 10{sup 5 }V/m in the national spherical torus experiment (NSTX). The modelling shows a considerable reduction in X-B mode conversion efficiency, C{sub modelling} = 0.43, due to the presence of nonlinearities. Comparison of system properties to the linear state reveals predominant nonlinearmore » effects; EBW wavelength and group velocity in comparison with linear regime exhibit an increment around ∼36% and 17%, respectively.« less

Authors:
 [1];  [2]; ;  [1];  [3]
  1. Physics Department, Isfahan University of Technology, Isfahan 84156 (Iran, Islamic Republic of)
  2. (United States)
  3. Department of Electrical and Computer Engineering, Michigan State University, Michigan 48824-1226 (United States)
Publication Date:
OSTI Identifier:
22303438
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 21; Journal Issue: 9; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1070-664X
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; APPROXIMATIONS; BERNSTEIN MODE; COLD PLASMA; COMPARATIVE EVALUATIONS; EFFICIENCY; ELECTRONS; LANGMUIR FREQUENCY; MODE CONVERSION; NONLINEAR PROBLEMS; NSTX DEVICE; PLASMA WAVES; RADIOWAVE RADIATION; SIMULATION; SPHERICAL CONFIGURATION

Citation Formats

Ali Asgarian, M., E-mail: maliasgarian@ph.iut.ac.ir, E-mail: maa@msu.edu, Department of Electrical and Computer Engineering, Michigan State University, Michigan 48824-1226, Parvazian, A., Abbasi, M., and Verboncoeur, J. P. Direct X-B mode conversion for high-β national spherical torus experiment in nonlinear regime. United States: N. p., 2014. Web. doi:10.1063/1.4896706.
Ali Asgarian, M., E-mail: maliasgarian@ph.iut.ac.ir, E-mail: maa@msu.edu, Department of Electrical and Computer Engineering, Michigan State University, Michigan 48824-1226, Parvazian, A., Abbasi, M., & Verboncoeur, J. P. Direct X-B mode conversion for high-β national spherical torus experiment in nonlinear regime. United States. doi:10.1063/1.4896706.
Ali Asgarian, M., E-mail: maliasgarian@ph.iut.ac.ir, E-mail: maa@msu.edu, Department of Electrical and Computer Engineering, Michigan State University, Michigan 48824-1226, Parvazian, A., Abbasi, M., and Verboncoeur, J. P. Mon . "Direct X-B mode conversion for high-β national spherical torus experiment in nonlinear regime". United States. doi:10.1063/1.4896706.
@article{osti_22303438,
title = {Direct X-B mode conversion for high-β national spherical torus experiment in nonlinear regime},
author = {Ali Asgarian, M., E-mail: maliasgarian@ph.iut.ac.ir, E-mail: maa@msu.edu and Department of Electrical and Computer Engineering, Michigan State University, Michigan 48824-1226 and Parvazian, A. and Abbasi, M. and Verboncoeur, J. P.},
abstractNote = {Electron Bernstein wave (EBW) can be effective for heating and driving currents in spherical tokamak plasmas. Power can be coupled to EBW via mode conversion of the extraordinary (X) mode wave. The most common and successful approach to study the conditions for optimized mode conversion to EBW was evaluated analytically and numerically using a cold plasma model and an approximate kinetic model. The major drawback in using radio frequency waves was the lack of continuous wave sources at very high frequencies (above the electron plasma frequency), which has been addressed. A future milestone is to approach high power regime, where the nonlinear effects become significant, exceeding the limits of validity for present linear theory. Therefore, one appropriate tool would be particle in cell (PIC) simulation. The PIC method retains most of the nonlinear physics without approximations. In this work, we study the direct X-B mode conversion process stages using PIC method for incident wave frequency f{sub 0} = 15 GHz, and maximum amplitude E{sub 0} = 10{sup 5 }V/m in the national spherical torus experiment (NSTX). The modelling shows a considerable reduction in X-B mode conversion efficiency, C{sub modelling} = 0.43, due to the presence of nonlinearities. Comparison of system properties to the linear state reveals predominant nonlinear effects; EBW wavelength and group velocity in comparison with linear regime exhibit an increment around ∼36% and 17%, respectively.},
doi = {10.1063/1.4896706},
journal = {Physics of Plasmas},
issn = {1070-664X},
number = 9,
volume = 21,
place = {United States},
year = {2014},
month = {9}
}