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Experimental Study of the Upper Hybrid Echo in Plasmas

Bauer, L. O. (1968) Experimental Study of the Upper Hybrid Echo in Plasmas. Electron Tube and Microwave Laboratory Technical Report, 40. California Institute of Technology , Pasadena, CA. (Submitted)

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The two-pulse stimulated radiation of dense (10^9/cm^3 < ne ≤ 10^(11)/cm^3) nonuniform neon and argon afterglow plasma columns longitudinally immersed in a magnetic field is studied. The magnetic field is very homogeneous over the plasma volume (ΔB/B ~ .01%). If the S-band microwave pulses' center frequency is such that they resonantly excite a narrow band of plasma upper hybrid oscillations close to the maximum upper hybrid frequency of the column, strong two- pulse echoes are observed. This new echo process is called the upper hybrid echo. The echo spectrum, echo power and echo width were studied as a function of the pulse peak power P, pulse separation τ, relative density (ω_(po)/ω)^2, and relative cyclotron frequency (ω_(c)/ω). The complex but systematic variations of the echo properties as a function of the above-mentioned parameters are found to be in qualitative agreement with those predicted by a theory of Gould and Blum based upon a simple nonuniform unidimensional cold plasma slab model. The possible effects of electron neutral and electron ion collisions not retained in the theoretical model are discussed. The existence of a new type of cyclotron echo, different from that of Hill and Kaplan and not predicted by the Blum and Gould model is documented. It is believed to be also of a collective effect nature and can probably be described in terms of a theory retaining some hot plasma effects.

Item Type:Report or Paper (Technical Report)
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Additional Information:The author wishes to express his deep appreciation to Professor Roy W. Gould for his advice, interest and encouragement throughout this investigation. It is a pleasure to thank Mr. Fred Blum for his major part in a lively and fruitful collaboration. The author is also indebted to Professor Robert S. Harp and Dr. Fred Hinton for many stimulating discussions, to Mr. Reiner Stenzel for his help in some phases of design of the apparatus, and to Mr. James Downward and Mr. Dick Smith for their corrections of the manuscript. The assistance in the preparation and typing of the manuscript by my wife, Sabine, and Mrs. Ruth Stratton is gratefully acknowledged. The author would also like to thank the Council of Scientific Research of Switzerland for its partial financial assistance. This investigation was supported by the Office of Naval Research.
Group:Electron Tube and Microwave Laboratory
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Council of Scientific Research (Switzerland)UNSPECIFIED
Office of Naval Research (ONR)220(50)
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Electron Tube and Microwave Laboratory Technical Report40
Series Name:Electron Tube and Microwave Laboratory Technical Report
Issue or Number:40
Record Number:CaltechAUTHORS:20190402-164740398
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:94390
Deposited By: Melissa Ray
Deposited On:03 Apr 2019 14:49
Last Modified:03 Oct 2019 21:03

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