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Theoretical as well as numerical analyses of the full set of Maxwell's equations is carried out to study non-axisymmetric (m≠  0) guided modes in radially nonuniform helicon (HE) discharges. Unlike the axisymmetric (m = 0) modes, these modes reveal a non-reciprocal behavior with respect to the azimuthal direction. We develop the conditions for propagation and non-propagation of the various modes in the helicon parameter range, thereby focussing on the important role of the radial density gradient. Three types of modes occurring in different parameter ranges are described, i.e., the helicon (HE) mode, the electrostatic (ES) or Trivelpiece-Gould mode, and the locally coupled (LC) mode that is characterized by mode coupling (MC) in a certain region of the plasma density profile. In contrast to m=+1 modes, the parameter range of m=−1 modes is much more restricted as rather high densities are needed for the propagation of the helicon and LC modes. An important issue of the investigations is the rf power coupling and absorption via the various modes. Computations based on a simple antenna-plasma model show that the axial wavenumber of the antenna determines decisively which type of mode is excited. In case of LC mode excitation, the dominant role of the MC layer for the absorption is demonstrated. Finally, the rf power coupling to helicon modes is studied. The density limit for m=−1 helicon mode propagation and the narrow magnetic field profiles of these modes are the main reasons why the rf power absorption in helicon discharges occurs via m=+1 helicon modes. [ABSTRACT FROM AUTHOR]

Theoretical as well as numerical analysis of the full set of Maxwell's equations was carried out to study axisymmetric (m=0) as well as non-axisymmetric (m ≠ 0) guided modes in a helicon discharge (radius R). In detail, the propagation of various guided modes for conditions of strong radial inhomogeneity was treated. The m=1 helicon dispersion exhibits for kzR ≪ 1 a quadratic frequency dependence on the axial wavenumber, ω ∝ kzz, if the radial density gradient is steep enough. These modes reveal non-reciprocal behavior with respect to the azimuthal (θ) direction, that is, only modes with positive azimuthal mode numbers, m>0, can propagate. This is in contrast to the linear dispersion relation, ω ∝ kz (kzR ≪ 1), for common helicon mode propagation in weakly non-uniform plasma. The results agree reasonably with those obtained from the 2ndorder helicon wave equation derived for Ez=0. Furthermore, guided electrostatic (ES) modes were analyzed using the 2nd-order wave equation and their eigen mode spectrum was obtained. These modes reveal also non-reciprocal behavior with respect to θ and obey a quadratic dispersion law in strongly non-uniform plasma. A particular objective is mode coupling (MC) occurring when the helicon and the ES dispersion branches merge in a certain layer. For m=1 modes, mode coupling may arise at rather low density when the radial density gradient is steep enough. In any case, new modes, denoted as localized-coupled (LC) modes, may occur in the presence of an MC layer within the plasma. As for helicon and ES modes, the m=1 LC modes exhibit quadratic scaling in strongly non-uniform plasma. As a particular case, we examined the propagation of m=1 modes in a plasma column with a peaked density distribution in the center. The field distribution was found to be drastically altered due to mode coupling, thus leading to strongly enhanced wave absorption near the axis. [ABSTRACT FROM AUTHOR]

The oblique wave propagation in helicon-sustained plasma accounting for the effect of the radial electron density gradient is investigated. It is shown that the conditions for the conversion of electrostatic and electromagnetic modes may change drastically in strongly nonuniform helicon plasma due to modification of the wave dispersion branches. Furthermore, the densities at which mode conversion occurs can be considerably lower if the density gradient is steep enough. This result contrasts with the common mode conversion theory neglecting density gradient effects and predicting mode conversion in the central plasma region at very high electron densities. [ABSTRACT FROM AUTHOR]

Parametric instabilities arising in the pump field of a helicon wave are analyzed for typical parameters of helicon-produced plasmas. The pump wavenumber parallel to the magnetic field is assumed to be finite according to recent experimental findings obtained on a high-density helicon discharge. The parametric decay of the helicon pump wave into ion-sound and Trivelpiece–Gould waves is investigated. The approach takes into account that the damping rate of the Trivelpiece–Gould wave is generally much higher than the ion-sound frequency. The theoretical results are in agreement with the growth rates and thresholds of this instability, as well as the dispersion properties of the decay waves observed in helicon experiments. Estimates of the level of the decay parametric turbulence turn out to be sufficiently high to account for the strong absorption observed in helicon-produced plasmas. [ABSTRACT FROM AUTHOR]

It is demonstrated that the magnetization current, which arises from the interaction of high-frequency electromagnetic waves with hot collisionless, unmagnetized electron plasmas, can be derived by means of the ten-moment system of hydrodynamic equations. It is pointed out that the magnetization current is solely associated with the thermal motion of the electrons, and that it therefore does not appear in cold plasmas. This expression for the magnetization current agrees with those derived previously from kinetic theory. The present derivation provides, however, a comparatively much clearer physical picture of the origin of this current. In the limit where the phase velocity is much larger than the electron thermal velocity, a new result for the high-frequency induced vorticity of the plasma is obtained. It is also shown that the magnetization current in this paper is responsible for a novel scattering mechanism in which the high-frequency electromagnetic waves are scattered off vortex motions. [ABSTRACT FROM AUTHOR]

Discusses how the electron heating of radio frequency gas discharges is treated on the basis of quasilinear kinetic theory for characteristic scale lengths of the heating field much shorter than the electron mean free path. Consideration of plasmas bounded by walls providing specular reflection; Expressions for the coefficients of electron diffusion in energy space.

Presents a fluid model of surface wave that produced discharges for diffusion controlled regimes, taking into account simultaneously nonlinear contributions from stepwise ionization and volume recombination. Effect of saturation of metastable densities with growing electron density; Charged particle continuity and energy balance equations.

Examines the structural dynamics of a non-neutralized charged-particle beam based on the gas dynamics description. Spatial behavior of density for beams with a finite particle temperature; Constant axial velocity along the beam trajectory.