Theory of transverse surface electromagnetic waves propagating along a plasma-metal boundary with a finite radius of cur
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MA OSCILLATIONS AND WAVES
Theory of Transverse Surface Electromagnetic Waves Propagating along a Plasma–Metal Boundary with a Finite Radius of Curvature in a Magnetic Field V. A. Girka Karazin Kharkiv National University, pl. Svobody 4, Kharkiv, 61077 Ukraine Received April 21, 2005; in final form, June 2, 2005
Abstract—The spectra of electromagnetic waves propagating perpendicular to the axis of a plasma-filled metal waveguide in a magnetic field are studied with allowance for the effects exerted upon the wave frequency by the radial plasma density variation and by the emission of waves through a narrow axial slit in a waveguide wall. The case of wave propagation along the boundary between a plasma and a cylindrical metal waveguide wall with a periodically varying radius of curvature is also considered. The electromagnetic properties of the plasma are described by a dielectric tensor in the hydrodynamic approximation. The spatial distribution of the wave field is determined by the method of successive approximations. Results are presented from both analytical and numerical investigations. Analytical expressions for the corrections to the wave frequency due to the emission of the wave energy from the waveguide and due to the slight corrugation of the waveguide wall are obtained. The rates of wave damping due to the emission of the wave energy through a narrow axial slit and due to collisions between the plasma particles are found. The correction to the frequency that comes from the periodic variation of the radius of curvature of the plasma surface is calculated to within terms proportional to the square of the small parameter describing the azimuthal corrugation of the waveguide wall. The effect of the radial plasma density variation on the dispersion of the surface modes is examined both analytically and numerically. PACS numbers: 52.35.–g, 52.40.Fd DOI: 10.1134/S1063780X06050059
1. INTRODUCTION That surface waves (SWs) can propagate along a plasma–metal boundary was first suggested by Toda [1]. Since waveguides in which the plasma is in contact with a metal wall are widely used in laboratory experiments, their properties continue to be the subject of much investigation (see [2–4] and the literature cited therein). Such studies are especially important for the development of plasma technologies for material processing and for covering materials with special coatings by means of steady gas discharges [5–7]. Potential SWs [3] in plasma–metal waveguide structures have been studied fairly completely, but there is no complete theory of electromagnetic perturbations in such waveguides to date. Surface waves at the interface between a semi-bounded plasma and a metal were investigated in [3, 8–10] in plane geometry. For waveguides with small geometric dimensions, a plane boundary model is unsatisfactory, so it is necessary to take into account the curvature of the plasma surface. The effect of the corrugation of the waveguide wall on the dispersion of electromagnetic eigenmodes, as well as on the interaction of these mo
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