Radiation from electric and magnetic dipoles situated in a cavity formed by a plasma layer

Kovner, M. S.; Lapidus, V. A.; Lupanov, G. A.

doi:10.1007/bf01032903

Radiophys Quantum Electron

1971

DOI: 10.1007/bf01032903

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Radiation from electric and magnetic dipoles situated in a cavity formed by a plasma layer

M. S. Kovner¹,

V. A. Lapidus²,

G. A. Lupanov³

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Cited by 2 publications

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“…(21) that transmission coefficients (19) and (21) Variations in the current of a source surrounded by the plasma sheath can be estimated using the input impedance calculated by induced EMF method [10]. For this estimate, we need the coefficients of reflections of the field from the surface r = r 1 of the inner vacuum cylindrical cavity since the induced EMF is determined using the field component E x whose Fourier transform has the form…”

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Field of an electric dipole surrounded by a nonuniform cylindrical plasma sheath

Bichutskaya

Makarov

2007

Radiophys Quantum Electron

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We analyze and solve the problem of the field of a dipole surrounded by a cylindrical plasma sheath with a piecewise-linear profile of dielectric permittivity ε including the point at which ε = 0. The predominant influence of the region in which ε = 0 on the formation of the dipole field is shown. The resonant properties of the solution in the case of a small cross-sectional size of the cylindrical sheath are studied.An increase in the radiation from antennas sura Fig. 1.rounded by plasma sheathes of various shapes (circular or elliptic cylindrical, spherical, and spheroidal) for the same current as in the sheathless antenna was considered for the model of a plasma sheath in the form of a homogeneous or piecewise-homogeneous medium with a step-like transition of dielectric permittivity between a vacuum layer (ε = 1) and a plasma layer with the negative real part of dielectric permittivity [1][2][3][4][5][6]. In those works, the region in which the real part of dielectric permittivity went to zero was not considered, although this region predominantly affects the formation of the source field in the cases analyzed in [7,8]. In this paper, we study the influence of a plasma sheath on the source field within the framework of a model allowing for the transition region between a vacuum cavity and a plasma sheath. At first, we consider a model in which the transition is described by a piecewise-constant profile of dielectric permittivity with a zero real part. Then we study another plasma-sheath model in which the transition between a vacuum layer and a uniform plasma sheath is described by a linear profile of dielectric permittivity with the real part crossing zero.Let us pass to solving the first problem. Consider the radiation from an electric dipole located at the center of the cross section of an infinitely long cylindrical plasma column ( Fig. 1) with radius a such that the cross-sectional size of the cylinder is small (ka 1, where k = ω/c, ω is the angular frequency, and c is the speed of light). We assume that the dipole moment of the source located at the origin of a system of cylindrical coordinates (r, ϕ, z) is aligned with the column radius for z = 0 and ϕ = 0, i.e., the electric dipole is horizontal. Note that in the case of a dipole moment parallel to the axis of a plasma column, a resonant increase in the radiation field is absent [9]. The relative dielectric permittivity of the medium filling the cylindrical column is described by a piecewise-constant function ε p (r) (Fig. 2a) such that * Yulia.Afanasyeva@paloma.spbu.ru

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Field of an electric dipole surrounded by a nonuniform cylindrical plasma sheath

Bichutskaya

Makarov

2007

Radiophys Quantum Electron

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“…We now consider the influence of the boundaries between the plasma spheroid and the inner and outer vacuum regions on the input impedance Z [17] of the source. Note that in the case where the source is surrounded by a sphere with an arbitrary real dielectric permittivity ε, the presence of the boundaries leads to a considerable increase in the reactive part of the impedance in comparison with its real part [8]:…”

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Field of an Electric Dipole Surrounded by a Small Plasma Spheroid with a Cavity

Bichutskaya

Makarov

2005

Radiophys Quantum Electron

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We obtain and analyze a solution of the boundary-value problem for the field of an electric dipole centered in a vacuum cavity inside a small plasma spheroid. The influence of the cavity size on the field enhancement in an outer vacuum region is analyzed as a function of the curvature of the plasma-spheroid surface. The results are compared with the case of a sphere with similar cavity.This paper is the continuation of works [1][2][3][4][5][6][7][8][9][10][11][12] devoted to studying the influence of small plasma regions around a dipole source on its radiation into an outer vacuum region. Such studies are aimed at analyzing possibilities of enhancement of radiation from a small plasma region. The studies were performed for plasma regions of different shapes ranging from a circular or elliptic cylinder to a sphere and a prolate or oblate spheroid. The effect of the shape of a plasma Fig. 1.region was revealed and some estimates of the influence of an ion sheath formed around sources in plasmas [13,14] and modeled by a vacuum sheath were performed. The presence of a continuous isotropic plasma region [1-6] around a source leads to an increase in the field in an outer vacuum region by 1-2 orders of magnitude compared with the case where the plasma region is absent, provided the amplitude of the feeding current at a single resonant frequency determined by the plasma-region shape remains intact. The presence of an external magnetic field [7-10] or allowance for an ion sheath [11,12] around the source in plasma leads to splitting the resonant frequency into two frequencies and can enhance this effect.In this paper, we study the influence of the ion sheath on the far-zone field of a source surrounded by a plasma spheroid of small electrical sizes k p a 1, where k p = ω p /c, ω p is the electron plasma frequency, a is the major semiaxis of the spheroid, and c is the speed of light in free space.We consider the radiation field of an electric dipole centered in a small prolate plasma spheroid with the major and minor semiaxes a and b, respectively (Fig. 1), and the eccentricity e. The dipole is aligned with the symmetry axis of the spheroid. The ion sheath around the source is modeled by a small vacuum spheroid with the semiaxes a 1 and b 1 and the same eccentricity e. The model of an inner cavity with a sharp boundary is simplified and neglects the influence of the region with the relative dielectric permittivity ε = 0. We plan to consider this influence in future works. The distance 2d 1 between the foci of the inner spheroid is assumed to vary from the minimum value determined by the dipole length to the value almost * Yulia.Afanasyeva@paloma.spbu.ru

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Radiation from electric and magnetic dipoles situated in a cavity formed by a plasma layer

Cited by 2 publications

References 1 publication

Field of an electric dipole surrounded by a nonuniform cylindrical plasma sheath

Field of an electric dipole surrounded by a nonuniform cylindrical plasma sheath

Field of an Electric Dipole Surrounded by a Small Plasma Spheroid with a Cavity

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