Influence of a sample surface on single electrode atmospheric plasma jet parameters

• First report on reciprocal influence between helium plasma jet and sample surface
• Optical emission spectroscopy and electromagnetic measurements were performed.
• For characterization different samples of various sizes and conductivities were used.
• Discharge and plasma parameters vary with treated sample distance and its material.
• Even plasma jet treatment of solids produced new plasma species observable with OES.

The article reports on reciprocal influence between the sample surface and atmospheric plasma jet. This correlation is important since it changes plasma parameters and plasma itself, depending on the sample-material surface, presence of liquid or treatment distance. However, in experiments and treatments of surfaces with atmospheric plasma jets, this relationship is usually disregarded. In order to investigate reciprocal influence, we implemented electromagnetic and optical emission spectroscopy characterization of atmospheric plasma needle jet. Characterization was performed during treatment of various samples. We have shown that sample material and its distance from the tip of the electrode have a pronounced influence on atmospheric pressure plasma jet electromagnetic and optical characteristics, such as jet length, shape, color, voltage, current, power, electromagnetic field and concentrations of plasma species. It was shown that for a given flow there is a critical distance (≈ 15 mm) between the tip of the wire and the sample surface for which jet emission intensity, especially ionic, is at maximum.