PRODUCTION OF LARGE-AREA PLASMAS BY ELECTRON-BEAMS

An analysis is presented for the production of weakly ionized plasmas by electron beams, with an emphasis on the production of broad, planar plasmas capable of reflecting X-band microwaves. Considered first in the analysis is the ability of weakly ionized plasmas to absorb, emit and reflect electromagnetic radiation. Following that is a determinati on of the electron beam parameters needed to produce plasmas, based on considerations of beam ionization, range, and stability. The results of the analysis are then compared with a series of experiments perform ed using a sheet electron beam to produce plasmas up to 0.6 m square b y 2 cm thick. The electron beam in the experiments was generated using a long hollow-cathode discharge operating in an enhanced-glow mode. T hat mode has only recently been recognized, and a brief analysis of it is given for completeness. The conclusion of the study is that electr on beams can produce large-area, planar plasmas with high efficiency, minimal gas heating, low electron temperature, high uniformity, and hi gh microwave reflectivity, as compared with plasmas produced by other sources. (C) 1998 American Institute of Physics.