Dispersion studies of surface-wave-produced discharges with a view to diagnostics

Dispersion of surface-wave-produced plasmas and field behaviour outside the discharges are studied under the influence of collisions and radial and ax ial density inhomogeneities, the latter density, both in WKB and eigenfunct ion treatment, is carried through for a cylindrical discharge configuration . The trends of joint influences can be approximated by an extrapolation fr om WKB treatment, avoiding the large numerical effort of an accurate two-di mensional code. Some consequences for radiophysics diagnostics are pointed out. Whereas standard methods of phase measurements are only weakly affecte d, amplitude measurements are more subject to various influences. Therefore , potential extensions of methods using test waves of various frequencies c an yield additional and improved information on the collision frequency and on the value of the radial inhomogeneity index. A procedure is suggested a nd exemplified with measurements at a helium discharge.