Characterization of argon metastable species as function of time, space, and current of a pulsed dc glow discharge

Optical measurements performed through an iCCD camera equipped with an optical bandpass filter have been carried out on a pulsed dc glow discharge (GD) in order to study the spatial, temporal, and current dependency of the 1s5 (3P2) Ar metastable (Ar*) species. For the spatial and temporal study the pressure was held constant at 1 hPa. The combination of the iCCD camera with the bandpass filter has allowed to acquire time-resolved images of the Ar* in a spatial region between the cathode and the anode. Those measurements have been performed through optical emission and absorption spectroscopy and have shown that the Ar* during the powering phase of the pulsed GD maximize in a spatial region close to the cathode (ca. 1 mm) and that at the end of the pulsed GD, in the so-called afterglow region, the Ar* maximize in a spatial region far from the cathode (between 6–8 mm). Then they reach their maximum intensity within the first 100 μs and decay within 200–250 μs, both after the end of the GD. It has also been observed that the Ar* species increase by increasing current.