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 electron densities of and electron temperatures of eV in argon decreased by a factor of ten compared to the pressure before the discharge. These experimental results are compared with a simple axial diffusion model of ionization and neutral transport and agree qualitatively with calculated axial profiles of neutral pressure. The effects of cusped fields on neutral density profiles and plasma confinement are also examined.