Diode laser absorption and emission spectroscopy of a streamer discharge in an atmospheric pressure plasma jet

Research into atmospheric pressure plasma jets (APPJs) that are initiated via a self-sustaining streamer discharge has recently been driven by both their potential for applications to nonthermal material processing, and fundamental questions regarding the basic discharge mechanisms that drive this remarkably stable atmospheric pressure discharge. We have characterized a streamer-initiated atmospheric pressure plasma jet in a 5% Ar / 95% He carrier gas flowing into ambient air using tunable diode laser absorption spectroscopy together with photomultiplier-coupled optical emission spectroscopy and current/voltage measurements. Improvements in the stability of this APPJ have allowed us to isolate the streamer discharge component with a higher precision than we have previously reported, as the shot-to-shot jitter is now comparable to the optical detector bandwidths. This APPJ configuration is similar to that used in previous workl, with the difference that only a single ring electrode is used here. Optical transitions from He, Ar, and various air species were used to characterize the spatiotemporal evolution of the discharge. The optical detector was aligned with the output from an 811.53 nm tunable diode laser that was used to measure the line integrated density of the Ar ls5 metastable.