EXPERIMENTAL INVESTIGATION OF MICROWAVE PROPAGATION IN A PLASMA WAVEGUIDE
The phase characteristics of a backward-wave pass-band mode were measured in a circular waveguide, which is coaxial with a circular isotropic plasma column. The mode was idertified as an n = 1 surface wave. Zero temperature plasma waveguide theory, which predicts this mode quite accurately, shows that a simple relation exists between the lower cut-off frequency and the electron plasma frequency obtained from this relation, where the cut-off frequency is determined from a measurement of the phase characteristics, agrees well with an independent measurement of the plasma frequency using the well-known cavity perturbation method. Noise measurements on the n = 1 and the symmetric n = 0 modes indicate thnt the signal to noise ratio is independent of input signal power and is about 7 db for the n = 1 mode and varies from about 7 to greater than 30 db for the n = 0 mode. A simple model of the plasma is proposed that explains all the noise observations reported. A strong DC axial magnetic field was applied to the plasma and the phase characteristics of the perturbed TE/sub 11/ empty waveguide mode were measured and are presented. In this case, the two degenerate circularly polarized modes that constitute the TE/sub 11/ mode in an empty waveguide become non-degenerate and thus will have different phase characteristics. The results are in qualitative agreement with the theoretical work of others. R is demonstrated experimentally that as the magnetic field is reduced, at a given frequency, the propagation constants of the two modes approach each other and finally coincide at zero magnetic field. (Dissertntion abstr., 24: No. 9, March 1964)
- Research Organization:
- Originating Research Org. not identified
- NSA Number:
- NSA-18-021444
- OSTI ID:
- 4001780
- Resource Relation:
- Other Information: Thesis. Orig. Receipt Date: 31-DEC-64
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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