Passage of electromagnetic waves through the critical surface

Effect of flux surface curvature on the linear coupling of electron cyclotron waves in tokamak plasmas

“…In this case, the condi tion corresponds to the modes trapped in a nearly rectangular potential well. If the incident beam is entirely localized in the well, the effect of the well "walls" is minimal and the modes comprising the beam are close to harmonic functions, which corre sponds to plane parallel geometry [4][5][6]. In this case, the coupling coefficient depends weakly on the posi tion of the incident beam if the beam is localized between the points of intersection of the cut off sur faces.…”

“…IN A TOKAMAK PLASMA The key properties of O-X coupling can be quali tatively described in the geometrical optics approxi mation [1,[3][4][5][6][7][16][17][18]. In this case, the dispersion relation for a cold magnetized plasma can be written as follows [10]:…”

“…A general solution to the problem of wave transforma tion that accurately takes into account the specific fea tures of the plasma and magnetic field distributions in toroidal confinement systems has been found. The applicability range of the widely used plane parallel approximation [1,[3][4][5][6][7] and the approximation of intersecting flat cut off surfaces [8][9][10][11][12][13][14][15] have been investigated as applied to tokamaks. The proposed semianalytic method for constructing the solution allows for a further generalization to the cases of more complicated distributions of the plasma density and magnetic field.…”

“…Most theoretical results concerning the processes of linear wave conversion in the electron cyclotron fre quency range were obtained in the framework of a pe ω = ω pe ω one dimensional model, which assumes that the plasma density varies along one direction [1,[3][4][5][6][7]. In recent years, it has been understood that a one dimen sional approach can be insufficient to describe O-X coupling in actual toroidal devices [8][9][10][11][12][13].…”

On Influence of 2D Inhomogeneity on Electromagnetic Mode Conversion Near the Cut_Off Surfaces in Magnetized Plasmas

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Most of the analytical results in the theory of OX conversion are obtained in a slab geometry, in which the magnetic field is uniform and ID spatial inhomogeneity is related to a constant plasma density gradient [1][2][3][4]. For conventional OXB scheme in toroidal systems this approximation is generally valid for the nearequatorial launch of the 0 mode when plasma density and magnetic field gradients are parallel to each other in the transformation region.

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