2017 Volume 15 Pages 55-64
Dust figures can be used to visualize the distributions of positive and negative charges that remain on the surface of an insulator using two types of charged powder; one is attached to the insulator and positive charges, and the other is attached to negative charges. In this study, dust figures were used to visualize the spreading pattern of an atmospheric-pressure plasma jet when an insulator was irradiated with the plasma jet in air. Observation using a high-speed camera indicates that streamers existed in the plasma and served as a source of both positive and negative charges. An ebonite plate was used as an insulator. White rosin powder and red lead (colored orange) powder were used to obtain positive and negative charge diagrams, respectively. When the ebonite plate was irradiated with an atmospheric-pressure argon (Ar) plasma jet in air, a disc- or ring-shaped dust figure was formed because of the residual positive and negative charges. The shape and size of the dust figure depended on the spreading pattern of the plasma jet on the ebonite plate. The dependence of the dust figure formed by both charges on the irradiation time (1–60 s) and distance (2–40 mm) of the plasma, the applied voltage (4–10 kV), and the Ar gas flow rate (5 or 10 L/min)was determined. [DOI: 10.1380/ejssnt.2017.55]
