Transport of ground-state hydrogen atoms in a plasma expansion - art. no. 016411

The transport of ground-state atomic hydrogen in the expansion of a thermal plasma generated from an Ar-H-2 mixture is studied by means of laser-based diagnostic techniques. The flow of hydrogen atoms is investigated by two-p hoton excitation laser-induced fluorescence (LIF), whereas Ar atoms are pro bed by LIF as well as by UV Rayleigh scattering. The transport of Ar atoms can be fully understood in terms of a free jet flow; H atoms on the contrar y exhibit an anomalous behavior. In the course of the plasma expansion, hyd rogen atoms decouple from the argon fluid by a diffusion process as a direc t consequence of recombination of H atoms at the vessel walls. In this cont ribution it is shown, on the basis of experimental results, how plasma-surf ace interactions can strongly influence the flow pattern of an atomic radic al fluid.