Effect of the shape of the cross section of a plasma-dielectric interface on the dispersion properties of azimuthal surf
- PDF / 289,192 Bytes
- 11 Pages / 612 x 792 pts (letter) Page_size
- 11 Downloads / 140 Views
MA OSCILLATIONS AND WAVES
Effect of the Shape of the Cross Section of a Plasma–Dielectric Interface on the Dispersion Properties of Azimuthal Surface Modes O. I. Girka, V. O. Girka, I. O. Girka, and I. V. Pavlenko Karazin Kharkov National University, pl. Svobody 4, Kharkov, 61077 Ukraine Received February 20, 2006; in final form, April 18, 2006
Abstract—A theoretical study is made of the propagation of a packet of surface electromagnetic waves with a zero axial wavenumber in a circular-cross-section cylindrical metal waveguide partially filled with plasma in an axial magnetic field. The cross section of the plasma column is assumed to be noncircular. The effect of the noncircular shape of the plasma cross section on the dispersion properties of azimuthal surface modes is investigated by the method of successive approximations. The fields of the waves and their eigenfrequencies are determined to second order in a small parameter. PACS numbers: 52.35.-g, 52.40.Fd DOI: 10.1134/S1063780X0702002X
1. INTRODUCTION
All this shows that the study of electromagnetic eigenmodes in noncircular plasma-filled waveguide structures is an important problem. The results of such research can find applications in plasma electronics and plasma technologies based on gas discharges. The objective of the present paper is to investigate how the frequency spectrum and spectral content of a packet of azimuthally propagating electromagnetic eigenmodes depend on the shape of the cross section of a plasma column.
Waveguide structures (in particular, those with slowing-down elements such as combs, disks, etc.) are excited most efficiently at frequencies close to their eigenfrequencies [1–3]. This is the reason for interest in studying wave spectra of multicomponent magnetoactive waveguides with slowing-down elements. The use of such elements, among other things, makes it possible to increase the output power of microwave generators based on plasma-filled waveguides [4, 5]. Multicomponent waveguide structures are widely used in presentday microwave electronics [6–12]. In metal waveguides with various dielectric and semiconductor insertions, the number of eigenmodes is larger and the wave propagation has some specific features, such as the possible existence of surface modes.
2. FORMULATION OF THE PROBLEM We consider the propagation of electromagnetic waves in a perfectly conducting cylindrical metal chamber with a circular cross section of radius b (see Fig. 1). In the chamber, there is a column of a cold plasma separated from the chamber wall by a dielectric layer with the permittivity εd ≥ 1. An external constant uniform magnetic field is directed along the waveguide axis, B0 || Z. The wave propagates strictly transversely to the magnetic field. The waveguide is assumed to be uniform along the cylinder axis, ∂/∂z ≡ 0. Let us consider a plasma column with an arbitrary cross section whose radius R1(ϑ) varies with azimuthal angle ϑ according to the law
Extraordinary electromagnetic waves propagating across an external constant axial magnetic f
Data Loading...
