Spatial distribution of H atom density in high-density, helicon-wave H-2 plasmas measured by laser-induced fluorescence

Spatial distributions of H atom density in high-density, helicon-wave H-2 p lasmas were measured by (2 + 1)-photon laser-induced fluorescence spectrosc opy. In low-power, high-pressure discharges, hill-type distributions, i.e., the H atom density in the plasma column was higher than that in the outsid e region, were observed. The hill-type density distribution can be explaine d by known mechanisms of gas-phase reactions, diffusion, and surface loss o f H atoms. On the other hand, in high-power, low-pressure discharges, deep dips were observed in the spatial distribution of the H atom density. The d ip region corresponded to the location of the plasma column, suggesting sig nificant heating of H atoms.