Dipole Resonance Mode Research Articles

Electron Density and Temperature Decay in Mercury Afterglows

Abstract : Average electron number density and electron-temperature measurements are presented for the mercury vapor afterglow in a hot-cathode cylindrical discharge tube at a pressure range where ambipolar diffusion predominates. The average electron number density is measured using cylindrical microwave cavities in the TM010 and dipole resonance modes. The electron temperature is measured by means of a time-resolving 3.0-GHz radiometer. Three pressure regions are identified. The initially rapid electron-temperature decay occurring during the first 0.5 msec of the afterglow is pressure independent and is well explained by electron-ion elastic collisions. The slow electron temperature decay after 0.5 msec which occurs in the second pressure region is pressure dependent and is explained by a balance between energy gain from collisions of the second kind in the reaction e + triplet P(2) to triplet P(1) +e and losses due to electron-ion elastic collisions. A complete discussion of these processes is given and the neglect of other mechanisms justified. (Author)

On the Dipole Resonant Mode of an Ionized Gas Column

In a recent paper, Makinson and Slade (1954) examined theoretically the scattering of a transverse-electric radio wave by an ionized gas column. In their treatment, a smooth radial distribution of ion density was replaced by a stepped approximation and the quasi-static equations (Kaiser and Closs 1952) were used to consider scattering by this stepped column. They claim that there exists a multiplicity of resonant dipole modes for a small cylindrical column in which the radial distribution of ionization is described by a Gaussian function. Previously, Kaiser and Closs (1952) had found a single, broad resonance peak by an approximate numerical solution of the quasi-static equations, using the Gaussian distribution itself. The purpose of this note is to suggest that the multiple resonances found by Makinson and Slade were created by the discontinuities in their approximation to the Gaussian function, and that the actual Gaussian distribution exhibits only one resonance.

Dipole Resonant Modes of an Ionized Gas Column

It is shown by a quasi-static treatment there is not one but a multiplicity of plasma resonant modes which will emit dipole radiation in a cylindrical column of ionized gas with a radially symmetrical but non-uniform electron density. It is shown that the multiple resonances obtained by Romell in scattering of short waves from a gas discharge column may be qualitatively explained assuming a reasonable electron distribution.