HELICON WAVE COUPLING TO A FINITE PLASMA-COLUMN

Inductive helicon wave coupling to a plasma column is studied numerically. In our theoretical model, the RF current distribution of the launching antenna is taken into account as well as the finite size of the plasma cylinder. Computational results based on the data of present-day helicon devices are shown. The efficiency of various types of antennae is studied for a wide range of experimental parameters. In particular, we discuss the role of magnetic-field-aligned electron Landau damping for the helicon wave absorption. In many cases, the numerical findings can be understood reasonably in terms of the wavenumber spectra of the antenna and the helicon wave dispersion relation. In general, however, the full electromagnetic treatment is necessary in order to describe and to understand the inductive coupling in the helicon wave regime.