Experiments on helicon plasma sources

This work concerns a search for novel plasma generators with applications to materials processing and advanced accelerators and radiation sources. Experimental measurements, together with a summary of the theory, are presented on the production of high-density plasmas using radio-frequency (rf) excitation of helicon waves. Plasma densities above 3 × 1013 cm−3 have been achieved with 2 kW of rf power. The required power agrees with classical diffusion theory. The scaling of density with magnetic field agrees with the theory of helicon waves. The effect of different antenna designs is demonstrated. Unexpected observations include: (a) a density maximum occurring at very low magnetic fields, (b) an increase in peak density with nonuniform fields, and (c) the strong effects of dc wall potentials on the behavior of the discharge. Tentative explanations of these phenomena are presented.