AXIAL STRUCTURE OF A SHIELDED PLASMA-COLUMN SUSTAINED BY A DIPOLAR ELECTROMAGNETIC-WAVE

We consider a low-pressure plasma column contained in a dielectric tub e surrounded by vacuum and shielded by a metal enclosure. The plasma i s sustained by a travelling, weakly damped electromagnetic dipolar wav e. The metal shielding turns out to influence substantially the disper sion characteristics and hence the axial structure of the discharge in contrast to the case of azimuthally symmetric waves. Axial profiles o f the electron number density and wave power have been calculated. A c omparison with the available experimental data shows the significance of the non-uniform radial plasma density profile for this configuratio n, which is taken into account by replacing the actual electron-neutra l collision frequency for momentum transfer by a greater effective val ue. It is determined by applying a scaling procedure (which is not a c urve fitting) that refers to a single experimental point. Thus a very good agreement between theory and experiment has been obtained.