Temporal and spatially resolved laser-scattering plasma diagnostics for the characterization of a ms-pulsed glow discharge

A previously described instrument was used to obtain axial profiles of the gas-kinetic temperature (T_g) in a ms-pulsed glow discharge via Rayleigh scattering. In addition, the electron number density (n_e) and the electron temperature (T_e) were observed via Thomson scattering. For these measurements, the detection optics of the original instrument were modified and a photon-counting imaging technique was employed to allow the simultaneous observation of Thomson scattering from multiple spatial positions. It was found that the cell pressure and electrical characteristics of the glow-discharge pulse have an effect on the temporal behavior of all fundamental parameters. As with a dc glow discharge, there were two distinct classes of electrons, a high-energy group and a lower-energy (thermalized) group. The thermalized electrons showed greater energies during the prepeak than at the plateau. Following the power pulse, during the afterglow, n_e and T_e declined monotonically at the temporal and spatial positions observed. The spatial differences in n_e during the afterglow are discussed with regards to the spatial variations in argon metastable population.