4 Conclusions
Surfatron plasma, similarly to other plasma jet discharges, exhibits strong inhomogeneity along the axis of discharge outside the discharge tube. While inside the tube only a negligible amount of admixtures intrudes the argon plasma, mixing of effluent plasma outside the tube with the surrounding atmosphere results in significant changes of the plasma and the emissions of molecular admixtures become comparable in intensity to the argon lines. From spatially resolved 2D intensity profiles of OH, NH, N2+ and Hα emissions, it can be seen that their relative intensity maximums are at different positions.
Table
The gas temperature was estimated from resolved OH radical spectra using the Boltzmann plot technique. It was found that the temperature of the effluent plasma is higher than the temperature inside the discharge tube, due to the presence of molecular admixtures. The effects of varying plasma properties along the discharge axis were examined also by plasma surface treatment of various samples. While the results for silicon and aluminium were sufficiently good even in the plasma flame end, the optimal position for stainless steel is close to the discharge tube end and prolonging the treatment time helped to decrease water and glycerol contact angles below 10° and thus achieve very good hydrophilic properties.