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Title: Resonance in Fast-Wave Amplitude in the Periphery of Cylindrical Plasmas and Application to Edge Losses of Wave Heating Power in Tokamaks

Abstract

Heating magnetically confined plasmas using waves in the ion-cyclotron range of frequencies typically requires coupling these waves over a steep density gradient. This process has produced an unexpected and deleterious phenomenon on the National Spherical Torus eXperiment (NSTX): a prompt loss of wave power along magnetic field lines in front of the antenna to the divertor. Understanding this loss may be key to achieving effective heating and expanding the operational space of NSTX-Upgrade. Here, we propose that a new type of mode, which conducts a significant fraction of the total wave power in the low-density peripheral plasma, is driving these losses. We demonstrate the existence of such modes, which are distinct from surface modes and coaxial modes, in a cylindrical cold-plasma model when a half wavelength structure fits into the region outside the core plasma. The latter condition generalizes the previous hypothesis regarding the occurence of the edge losses and may explain why full-wave simulations predict these losses in some cases but not others. If valid, this condition implies that outer gap control is a potential strategy for mitigating the losses in NSTX-Upgrade in addition to raising the magnetic field or influencing the edge density.

Authors:
ORCiD logo ; ; ORCiD logo ; ORCiD logo ; ORCiD logo
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Publication Date:
DOE Contract Number:  
AC02-09CH11466
Product Type:
Dataset
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Magnetically confined fusion Wave heating Cold plasma waves
Keywords:
Magnetically confined fusion Wave heating Cold plasma waves
OSTI Identifier:
1366752
DOI:
10.11578/1366752

Citation Formats

Perkins, R.J, Hosea, J.C., Bertelli, N., Taylor, G., and Wilson, J.R. Resonance in Fast-Wave Amplitude in the Periphery of Cylindrical Plasmas and Application to Edge Losses of Wave Heating Power in Tokamaks. United States: N. p., 2016. Web. doi:10.11578/1366752.
Perkins, R.J, Hosea, J.C., Bertelli, N., Taylor, G., & Wilson, J.R. Resonance in Fast-Wave Amplitude in the Periphery of Cylindrical Plasmas and Application to Edge Losses of Wave Heating Power in Tokamaks. United States. doi:10.11578/1366752.
Perkins, R.J, Hosea, J.C., Bertelli, N., Taylor, G., and Wilson, J.R. 2016. "Resonance in Fast-Wave Amplitude in the Periphery of Cylindrical Plasmas and Application to Edge Losses of Wave Heating Power in Tokamaks". United States. doi:10.11578/1366752. https://www.osti.gov/servlets/purl/1366752. Pub date:Fri Jul 01 00:00:00 EDT 2016
@article{osti_1366752,
title = {Resonance in Fast-Wave Amplitude in the Periphery of Cylindrical Plasmas and Application to Edge Losses of Wave Heating Power in Tokamaks},
author = {Perkins, R.J and Hosea, J.C. and Bertelli, N. and Taylor, G. and Wilson, J.R.},
abstractNote = {Heating magnetically confined plasmas using waves in the ion-cyclotron range of frequencies typically requires coupling these waves over a steep density gradient. This process has produced an unexpected and deleterious phenomenon on the National Spherical Torus eXperiment (NSTX): a prompt loss of wave power along magnetic field lines in front of the antenna to the divertor. Understanding this loss may be key to achieving effective heating and expanding the operational space of NSTX-Upgrade. Here, we propose that a new type of mode, which conducts a significant fraction of the total wave power in the low-density peripheral plasma, is driving these losses. We demonstrate the existence of such modes, which are distinct from surface modes and coaxial modes, in a cylindrical cold-plasma model when a half wavelength structure fits into the region outside the core plasma. The latter condition generalizes the previous hypothesis regarding the occurence of the edge losses and may explain why full-wave simulations predict these losses in some cases but not others. If valid, this condition implies that outer gap control is a potential strategy for mitigating the losses in NSTX-Upgrade in addition to raising the magnetic field or influencing the edge density.},
doi = {10.11578/1366752},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2016},
month = {7}
}

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Works referenced in this record:

Resonance in fast-wave amplitude in the periphery of cylindrical plasmas and application to edge losses of wave heating power in tokamaks
journal, July 2016

  • Perkins, R. J.; Hosea, J. C.; Bertelli, N.
  • Physics of Plasmas, Vol. 23, Issue 7
  • DOI: 10.1063/1.4954899

    Works referencing / citing this record:

    Resonance in fast-wave amplitude in the periphery of cylindrical plasmas and application to edge losses of wave heating power in tokamaks
    journal, July 2016

    • Perkins, R. J.; Hosea, J. C.; Bertelli, N.
    • Physics of Plasmas, Vol. 23, Issue 7
    • DOI: 10.1063/1.4954899