NEUTRAL PUMPING IN A HELICON DISCHARGE

At powers of 500-800 W of 13.56 MHz rf power in a 1 kG axial magnetic field, the neutral pressure in the bulk of a helicon discharge with el ectron densities of similar to 10(13) cm(-3) and electron temperatures of similar to 3 eV in argon decreased by a factor of ten compared to the pressure before the discharge. These experimental results are comp ared with a simple axial diffusion model of ionization and neutral tra nsport and agree qualitatively with calculated axial profiles of neutr al pressure. The effects of cusped fields on neutral density profiles and plasma confinement are also examined.