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Microwave absorption and emission from magnetized afterglow plasmas

Citation

Stenzel, Reiner L. (1970) Microwave absorption and emission from magnetized afterglow plasmas. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:07232014-095313314

Abstract

The microwave scattering properties of an axially magnetized afterglow plasma column in an S-band waveguide have been investigated experimentally. The column axis is perpendicular to the electric field and the direction of wave propagation in the H_(10)-mode waveguide. Strong absorption is found in the range of upper hybrid frequencies, ω_c ≤ ω ≤ [ω^2_c + ω^2_p(r,t)]^(1/2) where ω_c is the electron cyclotron frequency and ω_p is the locally and temporally varying electron plasma frequency. With the high absorption the noise emission approaches the blackbody limit. A microwave radiometer has been used to measure the noise power and with a comparison and null-technique the electron temperature. As emission and absorption are largely confined to a resonant layer, spatially resolved temperature data are obtained. Time resolution is obtained by gating the radiometer. The peak electron density is derived from the emission or absorption onset at the maximum upper hybrid frequency and confirmed by independent measurements. With this diagnostic technique the electron density and temperature decay has been studied under a variety of experimental conditions. Ambipolar diffusion and collisional cooling essentially account for the plasma decay, but impurities and metastable ions play an important role. The diagnostic method is successfully applied in a microwave heating experiment. The existence of absorbing resonant layers is shown by a peak in the radial temperature profile where the local upper hybrid frequency equals the heating frequency. The knowledge of the plasma parameters is important in the study of hot plasma effects. Buchsbaum-Hasegawa modes are investigated in a wide range of magnetic fields (.5 < ω_c/ω < .985).

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Electrical Engineering
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Electrical Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Gould, Roy Walter
Thesis Committee:
  • Unknown, Unknown
Defense Date:15 October 1969
Record Number:CaltechTHESIS:07232014-095313314
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:07232014-095313314
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8594
Collection:CaltechTHESIS
Deposited By: John Wade
Deposited On:23 Jul 2014 17:59
Last Modified:23 Jul 2014 17:59

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