Theory of a Slotted‐Sphere Antenna Immersed in a Compressible Plasma, Part III

The admittance of a slotted-sphere antenna immersed in a tenuous plasma was measured at frequencies between 35 and 110 MHz in the region of resonance of the probe-plasma system. A set of antennas with radii R between 0.8 and 3.2 em was used. The electron density and temperature were varied thus allowing studies to be made over a range of the parameter R!Lo from 6 to 30, where Lois the Debye length. The approximate theoretical model of Harp (1964) for the p9si_tion of the resonance was compared with measurements and was foun<1 to be adequate for values of (R/Lo) > 15. The width of the resonance line .:l was essentially independent of gas pressure for pressures bel;,w I0-3 Torr but wa:. found to be a strong function of R and L0 . The empirical relation (Ll(wp) where Wp is the plasma frequency, fits the observations. Some form of collisionless damping causes the observed line broadening.

Section: Resultsmentioning

confidence: 97%

“…Using Harp's model, the complex admittance Y of the slotted-sphere antenna is readily calculated (Smith and Bekefi, 1964; see also Wait, 1964Wait, , 1966 …”

Section: (Wr/wp)=fi[(afld); (Bfld); ---(S/ld); (V/wp)] (Wa/wp)=f2[(a/mentioning

confidence: 99%

RF Admittance Measurements of a Slotted‐Sphere Antenna Immersed in a Plasma

Waletzko¹,

Bekefi²

1967

“…This is a logical extension of the same problem treated in spherical geometry [Wait, 1964]. However, here we run into a basic difficulty because the angle functions associated with the electroacoustic waves are characteristically different from those of the electromagnetic waves.…”

Section: Spheroid Immersed In a Compressible Plasmamentioning

confidence: 96%

Theories of Prolate Spheroidal Antennas

Wait

1966

Self Cite

After reviewing some of the basic properties of spheroidal wave functions, the theory of radiation from a prolate spheroid antenna is considered. Particular attention is given to the complicating inftuence of a confocal plasma sheath whose properties may be either constant or depend on the polar angle coordinate. The effects of the compressibility of the plasma and the inftuence of a d-e magnetic field are also considered, using very idealized models. Among other things, it is indicated that a spheroidal structure may be strongly resonated (in a single mode) if the surface impedance has a special form.

“…Recently, the radiation of a longitudinal acoustic-type of wave in a compressible plasma has been studied by many investigators (e.g., Cohen, 1961;Whale, 1963;Seshadri, 1963;Wait, 1964). The analysis of the propagation of plane waves in a general plasma medium, studying the dispersion relations under many different conditions, has been worked out quite extensively (Oster, 1960;Ginzburg, 1961, Budden, 1961.…”

Section: Introductionmentioning

confidence: 99%

Dispersion Relation in Compressible Plasma

Wu¹

1967

The Maxwell‐Euler equations are reformulated through linear operator and generalized transform techniques into an equivalent matrix integral equation. The dispersion relation is obtained from the kernel of this integral equation for a homogeneous, anistropic, and compressible electron‐fluid plasma. Some illuminating graphs showing the propagation constants as functions of the normalized plasma frequency are developed analytically to study the dispersion relation. These kinds of graphs are usually plotted from the limited amount of numerical data available in the literature (e.g., Ginzburg, 1961). Clemmow‐Mullaly‐Allis type of diagram for the compressible plasma is sketched from these graphs. Actually, dispersion curves are obtained which are inversely related to the wave normal surfaces calculated by Allis, Buchsbaum and Bers (1963). A proper terminology for the three types of waves involved in an electron plasma is also introduced.