MODELING OF PROFILE EFFECTS FOR INDUCTIVE HELICON PLASMA SOURCES

A computer code for modeling existing and new helicon sources for mate rials processing has been developed, The Nagoya type-III, helical, and Stir coil antennas have been modeled to study and examine plasma dens ity and temperature profile effects on power absorption of a small fra ction (nfe/n(e) approximate to 5%) of fast electrons (T-e-fast approxi mate to 40 eV) which provide ionization of the neutral gas in the expe riment, and bulk (T-e-slow approximate to 3 eV) electron distributions in an argon gas, The ''ANTENA'' computer code, originally written by B. McVey to study ion cyclotron waves, was modified and used to study and model helicon sources, A collisional model that includes radial de nsity and temperature profiles was added to the code to study the effe ct of collisions on the heating mechanisms, The competing effects of c ollisional and Landau damping heating mechanisms have been investigate d in detail, and results indicate that collisions play an important ro le in the plasma absorption profile at high densities (n(e) greater th an or equal to 10(13) cm(-3)). The radio frequency wave absorption pro files are sensitive to the plasma density and temperature profiles, Th e partial-turn helix antenna, that solely excites the m = +1 azimuthal mode, is found to be more efficient in coupling the power to an assum ed plasma profile than the Nagoya type-III. The Stir coil is also foun d to be promising due to its on-axis peaking of the wave heating field s.