Detection of Trivelpiece-Gould modes in helicon discharges

Summary form only given. That helicon discharges produce higher plasma densities than unmagnetized inductively coupled plasmas (ICPs) is well known in the plasma processing community. A reason for the high RF coupling efficiency in these discharges has been suggested by Shamrai et al. (1997); namely, that helicon waves, though weakly damped themselves, can transfer their energy at the boundary to electrostatic electron cyclotron waves [called Trivelpiece-Gould (TG) modes in confined cylinders], and these, in turn, are rapidly damped as they propagate inward toward the axis. To test this hypothesis, we have performed an experiment to detect the TG waves directly.