Parametric study of two-dimensional potential structures induced by radio-frequency sheaths coupled with transverse currents in front of the Ion Cyclotron Resonance Heating antenna

Journal Article · Sat Apr 15 00:00:00 EDT 2006 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2186530· OSTI ID:20782748

Faudot, E; Heuraux, S; Colas, L ^[1]

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1. LPMIA, UMR CNRS 7040, Universite Henri Poincare, Nancy 1, BP 239, 54506 Vandoeuvre Cedex (France)

For the first time, a two-dimensional (2D) fluid model and an analytical expression for the rectified potential with respect to the transverse polarization current are established and verified by a 2D PIC (particle in cell) code over the validity domain of our model. Then the model is extended to the overall ion cyclotron frequency range used in different heating and current drive scenarios. First, the models demonstrate that these transverse polarization currents add some inertia in the temporal dynamic. Due to the nonlinear behavior of the I-V sheath characteristic, the time average amplitude (dc potential) of the rectified potential structure is increased compared to the time average rf potential. Second, they induce only a slight widening of the potential structure. Such modifications are quantified using a 'test map' initially characterized by a Gaussian shape. The map is assumed to remain Gaussian near its summit. The time behavior of the peak can be estimated analytically in the presence of polarization current as a function of its width r{sub 0} and amplitude {phi}{sub 0} (normalized to local temperature and to a characteristic length for transverse transport). A potential peaking criterion has been built to determine the peaking zone of the dc potential structure induced by the rf field. Computations made for typical parameters of the edge plasma in front of the antenna of the Tokamak Tore Supra show that the dc rectified potential is up to 50% higher than the previous computations neglecting polarization current effects. The weak diffused and high dc potential structures computed can explain the hot spot formation induced by convective cells associated to high energetic ion fluxes on the corners of the Ion Cyclotron Resonance Heating ant0010en.

• OSTI ID: 20782748
• Journal Information: Physics of Plasmas, Vol. 13, Issue 4; Other Information: DOI: 10.1063/1.2186530; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
AMPLITUDES
ANTENNAS
BOUNDARY LAYERS
CYCLOTRON FREQUENCY
ELECTRIC CURRENTS
HOT SPOTS
ICR HEATING
MOMENT OF INERTIA
NONLINEAR PROBLEMS
PARAMETRIC ANALYSIS
PLASMA
PLASMA CONFINEMENT
PLASMA POTENTIAL
PLASMA SHEATH
PLASMA SIMULATION
POLARIZATION
RADIATION TRANSPORT
RADIOWAVE RADIATION
RF SYSTEMS
TAIL IONS
TORE SUPRA TOKAMAK
TWO-DIMENSIONAL CALCULATIONS