Scattering of Radio Frequency Waves by Density Fluctuations in Tokamak Plasmas

Ram, A. K.; Hizanidis, K.; Ioannidis, Z.; Tigelis, I.

doi:10.7910/DVN/IX7AS3

Title: Scattering of Radio Frequency Waves by Density Fluctuations in Tokamak Plasmas

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Abstract

In tokamak fusion plasmas, coherent fluctuations in the form of blobs or filaments and incoherent fluctuations due to turbulence are routinely observed in the scrape-off layer. Radio frequency (RF) electromagnetic waves, excited by antenna structures placed near the wall of a tokamak, have to propagate through the scrape-off layer before reaching the core of the plasma. RF waves in the electron cyclotron and lower hybrid range of frequencies are commonly used to modify the current profile. In the International Thermonuclear Experimental Reactor (ITER), electron cyclotron waves are expected to stabilize the neoclassical tearing mode by providing current in the island region. While the effect of fluctuations on RF waves has not been quantified experimentally, there are telltale signs, arising from differences between results from simulations and from experiments, that fluctuations can modify the spectrum of RF waves. Consequently, pioneering theoretical studies and complementary computer simulations have been pursued to elucidate the impact of fluctuations on RF waves. These studies, using the full complement of Maxwell's equations for a cold, magnetized plasma, show that the Poynting flux in the wake of the filament develops spatial structure due to diffraction and shadowing. The uniformity of power flow into the plasma is affectedmore »« less

Authors:

Ram, A. K.; Hizanidis, K.; Ioannidis, Z.; Tigelis, I.

OSTI

Publication Date:: Thu Jan 10 04:00:00 UTC 2019

DOE Contract Number:: FG02-91ER54109; FG02-99ER54525; FC02-01ER54648

Research Org.:: Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center

Sponsoring Org.:: USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Subject:: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY

OSTI Identifier:: 1880856

DOI:: https://doi.org/10.7910/DVN/IX7AS3

Citation Formats


                    Ram, A. K., Hizanidis, K., Ioannidis, Z., and Tigelis, I. Scattering of Radio Frequency Waves by Density Fluctuations in Tokamak Plasmas.  United States: N. p., 2019. 
        Web.  doi:10.7910/DVN/IX7AS3.

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                    Ram, A. K., Hizanidis, K., Ioannidis, Z., & Tigelis, I. Scattering of Radio Frequency Waves by Density Fluctuations in Tokamak Plasmas.  United States.  doi:https://doi.org/10.7910/DVN/IX7AS3

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                    Ram, A. K., Hizanidis, K., Ioannidis, Z., and Tigelis, I. 2019.  
"Scattering of Radio Frequency Waves by Density Fluctuations in Tokamak Plasmas".  United States.  doi:https://doi.org/10.7910/DVN/IX7AS3.  https://www.osti.gov/servlets/purl/1880856. Pub date:Thu Jan 10 04:00:00 UTC 2019

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@article{osti_1880856,

  title        = {Scattering of Radio Frequency Waves by Density Fluctuations in Tokamak Plasmas},

  author       = {Ram, A. K. and Hizanidis, K. and Ioannidis, Z. and Tigelis, I.},

  abstractNote = {In tokamak fusion plasmas, coherent fluctuations in the form of blobs or filaments and incoherent fluctuations due to turbulence are routinely observed in the scrape-off layer. Radio frequency (RF) electromagnetic waves, excited by antenna structures placed near the wall of a tokamak, have to propagate through the scrape-off layer before reaching the core of the plasma. RF waves in the electron cyclotron and lower hybrid range of frequencies are commonly used to modify the current profile. In the International Thermonuclear Experimental Reactor (ITER), electron cyclotron waves are expected to stabilize the neoclassical tearing mode by providing current in the island region. While the effect of fluctuations on RF waves has not been quantified experimentally, there are telltale signs, arising from differences between results from simulations and from experiments, that fluctuations can modify the spectrum of RF waves. Consequently, pioneering theoretical studies and complementary computer simulations have been pursued to elucidate the impact of fluctuations on RF waves. These studies, using the full complement of Maxwell's equations for a cold, magnetized plasma, show that the Poynting flux in the wake of the filament develops spatial structure due to diffraction and shadowing. The uniformity of power flow into the plasma is affected by side-scattering, modifications to the wave spectrum, and coupling to plasma waves other than the incident RF wave. The Snell's law and the Fresnel equations have been reformulated within the context of magnetized plasmas. These are distinctly different from their counterparts in scalar dielectric media, and reveal new and important physical insight into the scattering of RF waves. All of these studies apply to the scattering of RF waves in any frequency range and for arbitrary variations in density.},

  doi          = {10.7910/DVN/IX7AS3},

  journal      = {},

  number       = ,

  volume       = ,

  place        = {United States},

  year         = {Thu Jan 10 04:00:00 UTC 2019},

  month        = {Thu Jan 10 04:00:00 UTC 2019}

}

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DOI: https://doi.org/10.7910/DVN/IX7AS3

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