Properties of plasmas generated by a single-turn antenna at lower-hybrid frequency

Summary form only given, as follows. A theoretical model of the plasmas generated by a sheath-helix antenna is developed for axisymmetric perturbations. The system configuration consists of a cylindrical plasma column inside a dielectric tube of radius R/sub c/. The eigenvalue equation is obtained and the eigenfunction is identified as the Bessel function J/sub 0/(x) of the first kind of order zero. The radial wave numbers /spl xi/ and /spl eta/ for the eigenfunction are described in terms of the rf frequency and plasma density. A full dispersion relation is analytically obtained, including the influence of finite plasma size. It is shown from the dispersion relation that the radial mode number /spl xi/ approaches infinity at the lower-hybrid frequency, exhibiting a resonance condition. Meanwhile, the radial wave number /spl eta/ approaches 3.83/R/sub c/ at the lower-hybrid frequency. A cross-sectional view of the light emission in experiment indicates that the helicon-plasma density at the lower-hybrid frequency has a hollow profile. The azimuthal component E/sub /spl theta//(r) of the perturbed electric field observed experimentally is very similar to the theoretical model of J/sub 1/(3.83r/R/sub c/) at the lower-hybrid frequency. The emission peak coincides with the radial location of the strongest electric-field intensity.