WAVE-PROPAGATION AND ABSORPTION SIMULATIONS FOR HELICON SOURCES

A two-dimensional (d-D), finite-difference computer code is developed to examine helicon antenna coupling, wave propagation, collisionless L andau, and collisional heating mechanisms. The code calculates the ele ctromagnetic wave fields and power absorption in an inhomogeneous, col d, collisional plasma. The current distribution of the launching anten na, which provides the full antenna spectra, is included in the model. An iterative solution that incorporates warm plasma thermal effects h as been added to the code to examine the contribution of collisionless (Landau) wave absorption by electrons. Detailed studies of the wave f ields and electron heating profiles at low magnetic fields (B-0 < 100 G), where both Trivelpiece-Gould (TG) and helicon modes are (H) presen t, are discussed. The effects of the applied uniform magnetic field (B -0 = 10-1000 G), 2-D (r, z) density profiles (n(e0) = 10(11)-10(13) cm (-3)), neutral gas pressures of 1-10 mTorr and the antenna spectrum on collisional and collisionless wave field solutions and power absorpti on are investigated. Cases in which the primarily electrostatic (TG) s urface wave dominates the heating and the power is absorbed near the e dge region and cases in which the propagating helicon wave transports and deposits its energy in the core plasma region are examined. (C) 19 98 American Institute of Physics. [S1070-664X(98)04812-5].