Hollow-Beam-Generated Plasma

摘要

Theoretical plasma density and potential radial profiles are derived for plasmas generated by a hollow electron beam. Both collision-dominated (with neutral atom) and collisionless plasmas are considered. Separate solutions of the region occupied by the cylindrical beam and the central region are first obtained. The two solutions are then matched at the inner radius of the beam to obtain the complete solution. Results indicate that plasma in the central region has essentially constant density and potential, while in the beam region both density and potential decrease monotonically with increasing radius. It is argued that the absence of any plasma particle sources or sinks in the central region is responsible for the relatively uniform plasma. Experimental results on a Penning Ionization Gauge discharge with an annular ring-shaped emitter confirm the uniform properties of the plasma in the hollow region. (Author)