Modeling of profile effects for inductive helicon plasma sources

A computer code for modeling existing and new helicon sources for materials processing has been developed. The Nagoya type-III, helical, and Stix coil antennas have been modeled to study and examine plasma density and temperature profile effects on power absorption of a small fraction (n/sub fe//n/sub e//spl ap/5%) of fast electrons (T/sub e-fast//spl ap/40 eV) which provide ionization of the neutral gas in the experiment, and bulk (T/sub e-slow//spl ap/3 eV) electron distributions in an argon gas. The "ANTENA" computer code, originally written by McVey (1984) to study ion cyclotron waves, was modified and used to study and model helicon sources. A collisional model that includes radial density and temperature profiles was added to the code to study the effect of collisions on the heating mechanisms. The competing effects of collisional and Landau damping heating mechanisms have been investigated in detail, and results indicate that collisions play an important role in the plasma absorption profile at high densities (n/sub c//spl ges/10/sup 13/ cm/sup -3/). The radio frequency wave absorption profiles are sensitive to the plasma density and temperature profiles. The partial-turn helix antenna, that solely excites the m=+1 azimuthal mode, is found to be more efficient in coupling the power to an assumed plasma profile than the Nagoya type-III. The Stix coil is also found to be promising due to its on-axis peaking of the wave heating fields.