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Investigation of RF Emissions from Electric Field Dominated Plasmas

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Final scientific rept. 1 Jan 1980-31 Mar 1989

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Research include effort to confirm the theory of the geometric mean plasma emission. This process results from two interpenetrating electron beams in a Penning discharge. Effort were made on diagnostic and software development for the study of plasma turbulence, automatic reduction of Langmuir probe data, and correlation studies of plasma fluctuations and turbulence using digital time series analysis techniques based on the fast Fourier transform. The methods of chaos theory are applied to the investigation of plasma turbulence, using a commercially available software program. Extensive studies were conducted of fluctuations in our highly turbulent Penning discharge. By perturbing the plasma with a signal of known amplitude and frequency applied to an effector probe. To one can demonstrate the enhancement of plasma turbulence and the resulting turbulent heating of the plasma electron andor ion population. These active modification experiments also demonstrated conditions under which a low frequency modulation of the plasma by the effector probe could dampen the turbulent modes present in the unmodulated plasma. The damping of turbulent modes at higher frequencies, above 50 kilohertz, was as high as 10 to 20 db in some instances. This suggests a way to actively modify plasma turbulence and affect or reduce transport parameters which depend on the level of plasma turbulence. A diagnostic procedure was developed for measuring the effective collision frequency of electrons in plasmas due not only to binary collisions with other electron or neutral atoms, but also to turbulent collisions of the electrons which result when the electrons scatter off fluctuating electric fields in our plasma.

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  • Plasma Physics and Magnetohydrodynamics

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