Electrical and optical characterization of a wide plasma brush in atmospheric helium flow

Summary form only given. It is well known that atmospheric gas discharges are prone to instabilities leading to the glow-to-arc transition, particularly when reactive gases are introduced to facilitate their applications. One technique to overcome plasma instabilities is to separate the region of plasma generation from that of plasma processing with the two regions linked through a suitable plasma transportation. One example is atmospheric pressure plasma jets, which typically have a diameter in the millimeter range. Where these are well suited for local treatment of surfaces, they are less effective for processing of large-scale surfaces. To this end, it is desirable to explore ways to increase the cross-sectional area of such plasma jets. In this contribution, we report a plasma slot jet in atmospheric helium flow, with or without oxygen admixture. The slot jet has a width of 2.5 cm, and can be up-scaled further to above 5cm. It appears like a plasma brush, and offers greater surface coverage. While such slot jet configurations may lead to streamers, we have studied plasma stability using nanosecond imaging and explored ways to improve plasma stability by means of (1) electrode dimensions; (2) flow rate; (3) excitation frequency. Electrical characterization has also been performed, and suggested that there exist two different modes, depending on the electrode configuration and dimensions. To characterize the production of reactive plasma species, optical emission spectroscopy has been used. These studies provide a useful basis from which to assess and develop the plasma brush for a number of applications.