Accession Number : ADA273826

Title :   Diffusion in Electronegative Discharges with Magnetic Fields.

Descriptive Note : Doctoral thesis,

Corporate Author : AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH

Personal Author(s) : Bell, David E.

Report Date : 03 DEC 1993

Pagination or Media Count : 207

Abstract : Electronegative plasmas are important in a variety of electric discharge applications, such as plasma reactors, negative ion sources, and even electropositive discharges when contaminated with an electronegative impurity. The need for an understanding of the processes and phenomena associated with these electronegative discharges has spurred the development of numerical simulations and models. While many of the devices incorporate various configurations of external magnetic fields, specific attention to the influence of the magnetic field on the discharge operating point, structure, and stability is lacking. To address this deficiency, a collisional model for diffusion in three-component plasmas with an applied magnetic field is developed; it is an extension of Schottky theory allowing for negative ions and a magnetic field. This study analyzes the effect of magnetic fields on diffusion in three-component plasmas; provides an analytic solution for the collisional model in a magnetic field; evaluates the validity of effective diffusion coefficients through an analysis of the afterglow; and provides a regime of validity for the model in terms of magnetic field strength by looking at the onset of anomalous diffusion. Electronegative discharge, Ambipolar diffusion, Helical instability, Afterglow, Magnetic field.

Descriptors :   *DIFFUSION, *MAGNETIC FIELDS, AFTERGLOWS, COEFFICIENTS, CONFIGURATIONS, DEFICIENCIES, ELECTRIC DISCHARGES, EXTERNAL, IMPURITIES, INSTABILITY, ION SOURCES, MODELS, SIMULATION, STABILITY, STRUCTURES, THESES, PLASMA DEVICES, NUMERICAL ANALYSIS, COLLISIONS.

Subject Categories : Electricity and Magnetism
      Physical Chemistry
      Plasma Physics and Magnetohydrodynamics
      Atomic and Molecular Physics and Spectroscopy

Distribution Statement : APPROVED FOR PUBLIC RELEASE