Multi-diagnostic approach to energy transport in an atmospheric pressure helium-oxygen plasma jet

The energy balance of a plasma holds fundamental information not only about basic plasma physics, but it is also important for tailoring plasmas to specific applications. Especially RF-driven atmospheric pressure plasma jets (APPJs) operated in helium with oxygen admixture have high application potential in industry and medicine. Many types of plasma jets have been studied up to now, leading to the challenge how to compare results from various sources. We have developed a method for measuring the power deposited in the plasma as the parameter to compare different sources and gas mixtures with each other. Furthermore, we studied energy transport as a function of this input power and molecular gas admixture in a newly developed APPJ based on the COST-reference jet with a capillary as a dielectric in between the electrodes. The gas temperature, atomic oxygen density, ozone density and absolute emission intensity in the visible wavelength range have been determined. Combining the results gave an energy balance with most of the energy deposited into gas heating. Production of final chemical products made up a small amount of the deposited power while radiation was negligible for all combinations of external parameters studied.