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Title: External excitation of a short-wavelength fluctuation in the Alcator C-Mod edge plasma and its relationship to the quasi-coherent mode

Abstract

A novel “Shoelace” antenna has been used to inductively excite a short-wavelength edge fluctuation in a tokamak boundary layer for the first time. The principal design parameters, k{sub ⊥}=1.5±0.1 cm{sup −1} and 45<300 kHz, match the Quasi-Coherent Mode (QCM, k{sub ⊥}∼1.5 cm{sup −1}, f∼50−150 kHz) in Alcator C-Mod, responsible for exhausting impurities in the steady-state, ELM-free Enhanced D{sub α} H-mode. In H-mode, whether or not there is a QCM, the antenna drives coherent, field-aligned perturbations in density, n{sup ~}{sub e}, and field, B{sup ~}{sub θ}, which are guided by field lines, propagate in the electron diamagnetic drift direction, and exhibit a weakly damped (γ/ω{sub 0}∼5%−10%) resonance near the natural QCM frequency. This result is significant, offering the possibility that externally driven modes may be used to enhance particle transport. In L-mode, the antenna drives only a non-resonant B{sup ~}{sub θ} response. The facts that the driven mode has the same wave number and propagation direction as the QCM, and is resonant at the QCM frequency, suggest the antenna may couple to this mode, which we have shown elsewhere to be predominantly drift-mode-like [B. LaBombard et al., Phys. Plasmas 21, 056108 (2014)].

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ;  [1]
  1. Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)
Publication Date:
OSTI Identifier:
22252832
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 21; Journal Issue: 5; 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; ALCATOR DEVICE; ANTENNAS; BOUNDARY LAYERS; EDGE LOCALIZED MODES; ELECTRONS; EXCITATION; FLUCTUATIONS; H-MODE PLASMA CONFINEMENT; L-MODE PLASMA CONFINEMENT; PLASMA; PLASMA IMPURITIES; WAVELENGTHS

Citation Formats

Golfinopoulos, T., LaBombard, B., Parker, R. R., Burke, W., Davis, E., Granetz, R., Greenwald, M., Irby, J., Leccacorvi, R., Marmar, E., Parkin, W., Porkolab, M., Terry, J., Vieira, R., and Wolfe, S. External excitation of a short-wavelength fluctuation in the Alcator C-Mod edge plasma and its relationship to the quasi-coherent mode. United States: N. p., 2014. Web. doi:10.1063/1.4873595.
Golfinopoulos, T., LaBombard, B., Parker, R. R., Burke, W., Davis, E., Granetz, R., Greenwald, M., Irby, J., Leccacorvi, R., Marmar, E., Parkin, W., Porkolab, M., Terry, J., Vieira, R., & Wolfe, S. External excitation of a short-wavelength fluctuation in the Alcator C-Mod edge plasma and its relationship to the quasi-coherent mode. United States. https://doi.org/10.1063/1.4873595
Golfinopoulos, T., LaBombard, B., Parker, R. R., Burke, W., Davis, E., Granetz, R., Greenwald, M., Irby, J., Leccacorvi, R., Marmar, E., Parkin, W., Porkolab, M., Terry, J., Vieira, R., and Wolfe, S. 2014. "External excitation of a short-wavelength fluctuation in the Alcator C-Mod edge plasma and its relationship to the quasi-coherent mode". United States. https://doi.org/10.1063/1.4873595.
@article{osti_22252832,
title = {External excitation of a short-wavelength fluctuation in the Alcator C-Mod edge plasma and its relationship to the quasi-coherent mode},
author = {Golfinopoulos, T. and LaBombard, B. and Parker, R. R. and Burke, W. and Davis, E. and Granetz, R. and Greenwald, M. and Irby, J. and Leccacorvi, R. and Marmar, E. and Parkin, W. and Porkolab, M. and Terry, J. and Vieira, R. and Wolfe, S.},
abstractNote = {A novel “Shoelace” antenna has been used to inductively excite a short-wavelength edge fluctuation in a tokamak boundary layer for the first time. The principal design parameters, k{sub ⊥}=1.5±0.1 cm{sup −1} and 45<300 kHz, match the Quasi-Coherent Mode (QCM, k{sub ⊥}∼1.5 cm{sup −1}, f∼50−150 kHz) in Alcator C-Mod, responsible for exhausting impurities in the steady-state, ELM-free Enhanced D{sub α} H-mode. In H-mode, whether or not there is a QCM, the antenna drives coherent, field-aligned perturbations in density, n{sup ~}{sub e}, and field, B{sup ~}{sub θ}, which are guided by field lines, propagate in the electron diamagnetic drift direction, and exhibit a weakly damped (γ/ω{sub 0}∼5%−10%) resonance near the natural QCM frequency. This result is significant, offering the possibility that externally driven modes may be used to enhance particle transport. In L-mode, the antenna drives only a non-resonant B{sup ~}{sub θ} response. The facts that the driven mode has the same wave number and propagation direction as the QCM, and is resonant at the QCM frequency, suggest the antenna may couple to this mode, which we have shown elsewhere to be predominantly drift-mode-like [B. LaBombard et al., Phys. Plasmas 21, 056108 (2014)].},
doi = {10.1063/1.4873595},
url = {https://www.osti.gov/biblio/22252832}, journal = {Physics of Plasmas},
issn = {1070-664X},
number = 5,
volume = 21,
place = {United States},
year = {Thu May 15 00:00:00 EDT 2014},
month = {Thu May 15 00:00:00 EDT 2014}
}