Phd records
https://feeds.library.caltech.edu/people/Stenzel-R-L/Phd.rss
A Caltech Library Repository Feedhttp://www.rssboard.org/rss-specificationpython-feedgenenWed, 31 Jan 2024 19:51:18 +0000Microwave absorption and emission from magnetized afterglow plasmas
https://resolver.caltech.edu/CaltechTHESIS:07232014-095313314
Authors: {'items': [{'id': 'Stenzel-R-L', 'name': {'family': 'Stenzel', 'given': 'Reiner L.'}, 'show_email': 'NO'}]}
Year: 1970
DOI: 10.7907/PFRP-ZW64
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).
https://thesis.library.caltech.edu/id/eprint/8594