Propagation of m=-1 mode helicon waves

Summary form only given. Helicon waves are plasma waves in the whistler frequency regime which are excited in a bounded plasma. These waves have demonstrated the capability of propagation at high plasma densities (/spl sim/10/sup 13/ cm/sup -3/) at powers less than 1 kW. While theory allows for the existence of various azimuthal modes, most experiments have produced primarily m=0, +1. However, field patterns for the m=-1 mode indicate that this mode could achieve higher centerline densities than the m/spl ges/0 modes. Theoretical and computational modelling of helicon propagation using the ANTENA code indicate the existence of a cutoff density for the m=-1 mode which is higher than the typical densities achieved in experiments. Unlike the more common 0 and +1 modes, m=-1 helicon waves are difficult to create since the mode is unable to initially create the high densities needed to maintain it. If the other modes are able to establish a density greater than the -1 cutoff, this mode can then be established. This threshhold density is exceeded in our experiments through the use of edge limiters to create a narrow, steady state high density plasma. The helicon plasma dispersion relation predicts peak plasma density will vary inversely with plasma radius.