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

Perkins, R. J.; Hosea, J. C.; Bertelli, N.; Taylor, G.; Wilson, J. R.

doi:10.1063/1.4954899

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. Furthermore, 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:

^[1]; Hosea, J. C. ^[1]; Bertelli, N. ^[1];

^[1];

^[1]

Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA

Publication Date:: Fri Jul 01 00:00:00 EDT 2016

Research Org.:: Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

Sponsoring Org.:: USDOE

OSTI Identifier:: 1257631

Alternate Identifier(s):: OSTI ID: 1263692

Grant/Contract Number:: AC02-09CH11466

Resource Type:: Accepted Manuscript

Journal Name:: Physics of Plasmas

Additional Journal Information:: Journal Volume: 23; Journal Issue: 7; Journal ID: ISSN 1070-664X

Publisher:: American Institute of Physics (AIP)

Country of Publication:: United States

Language:: English

Subject:: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; wave heating; cold plasma waves

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:10.1063/1.4954899.

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                    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.  https://doi.org/10.1063/1.4954899

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                    Perkins, R. J., Hosea, J. C., Bertelli, N., Taylor, G., and Wilson, J. R. Fri .  
"Resonance in fast-wave amplitude in the periphery of cylindrical plasmas and application to edge losses of wave heating power in tokamaks".  United States.  https://doi.org/10.1063/1.4954899.  https://www.osti.gov/servlets/purl/1257631.

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@article{osti_1257631,

  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. Furthermore, 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          = {10.1063/1.4954899},

  journal      = {Physics of Plasmas},

  number       = 7,

  volume       = 23,

  place        = {United States},

  year         = {Fri Jul 01 00:00:00 EDT 2016},

  month        = {Fri Jul 01 00:00:00 EDT 2016}

}

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Figure 1: Model geometry and radial density profile.

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