Cold Homogeneous Plasma Research Articles

Current and Charge Distributions along an Antenna in a Cylinder of Cold Plasma

The analysis of the insulated antenna in a relatively dense medium is modified to apply to a thin cylindrical dipole antenna in a glass tube filled with a homogeneous cold plasma. Account is taken of the finite radius of the plasma column and of the thickness of the containing tube. Complex wavenumbers, distributions of current and charge, and driving-point admittances have been calculated for dipoles with electrical lengths up to two wavelengths. The effect of the thickness and permittivity of the glass tube on the wave number and admittance is determined. Numerous graphs and tables are provided.

Ion cyclotron wave generation in a two-ion plasma

Exact calculation of the dispersion relation of a cold plasma shows that the plasma behaviour is different from that predicted by the usual approximate theory which neglects electron inertia in the low-density limit. For example, the limiting value of Ω for optimum coupling is different from 1, where Ω is the wave frequency divided by the ion cyclotron frequency. This fact was ascertained experimentally in the QP-machine.Experimental observations of optimum coupling of the ion cyclotron wave in a two-ion plasma in the QP-machine are presented as functions of the plasma density. The plasma was produced by a PIG discharge with a density from 1010 to 2 × 1012 cm−3. The wave was generated by a Stix-type coil (coil wavelength 50 cm), which was fed by a 4.4-MHz, 20-kW oscillator. Experimental data lay within the band of H+ concentration between 10–90% of the dispersion relation of a homogeneous cold plasma column with a sharp boundary. However, the dependence of optimum loading on the diameter of the plasma column disagrees with the theoretical prediction.

Behaviour of separation constants for gyromagnetic plasmas

This note discusses the behaviour of separation Constants (which are also called transverse wave numbers) for electro magnetic-wave propagation in an anisotropic homogeneous cold plasma of arbitrary cross-section which is perpendicular to the direction of propagation (say z direction). Appropriate regions for which these constants are defined have been indicated in terms of inequalities among the various parameters, including the propagation coefficient β in the z direction.

Scattering of electromagnetic waves by a cylindrical plasma in a steady magnetic field: II. Magnetically induced inhomogeneity effects

The scattering of a plane electromagnetic wave with normal incidence from a cold homogeneous anisotropic plasma cylinder was studied in part I. Comparison with experiments made with a plasma obtained in the positive column of a mercury discharge tube showed that these anisotropic effects were not important enough to explain the reflection behaviour.Because of the drift of the plasma along the axis, there is a magnetically induced asymmetrical inhomogeneity when the static magnetic field B0 lies in the cross-section of the cylinder. The solution of the problem of the inhomogeneity effects is purely TE as no coupling between TE and TM modes is introduced by the inhomogeneity. It is characteristic that the different angular modes (n = l, n = 2, n = 3, etc.) are coupled through the inhomogeneity. The magnetic field enhances thus the quadrupolar, hexapolar, etc. effects, in agreement with the experimental data. The inhomogeneity effects suffice to explain the experimental results obtained in reflection (TE mode); the experimental and theoretical electron density ratios corresponding to the first three (n = 1, 2 and 3) observable “cold plasma” peaks are in very striking agreement. As all the n angular modes are coupled, the chain is broken off in the theoretical computations by neglecting the coefficients of a given order n; this is satisfactory as these coefficients tend to zero when n tends to infinity.