Abstract：Atmospheric pressure dielectric barrier discharge (APDBD) has attracted significant interest in various fields as a result of its gentle and uniform generation of active species over a large surface area. However, the plasma characteristics, such as active species concentration, electron excitation temperature, and density, during different discharge modes are not clearly understood. In this study, a “voltage-flow co-control mechanism” is proposed to systematically explore the evolution of electronic parameters and discharge modes in helium APDBD plasma, aiming to provide theoretical support for the design of industrial-grade plasma sources. In this experiment, a ring-ring DBD reactor was utilized to investigate the dynamic characteristics of active particle concentration and electronic parameters using emission spectrum analysis and electrical diagnosis technology. It is found that the main active particles in atmospheric helium dielectric barrier discharge plasma include excited helium atom He I, hydrogen atom Hα, oxygen atom O I, hydroxyl OH (A-X), nitrogen molecule N+2 (B-X), excited nitrogen molecule N2 (C-B), and N2 (B-A). The Boltzmann slope method and Hα line Stark broadening were used to diagnose the electron excitation temperature (Te) and electron density (ne) of the plasma. It was found that the coupling mechanism between the discharge mode and the electronic parameters showed three stages of evolution: At a helium gas flow rate of 0.5 SLM and low voltage range of (9~11kV), APDBD demonstrated a uniform discharge mode with a 56% increase and 36% decrease in electron excitation temperature and density respectively. When the voltage was increased to medium range (11~15 kV), asymmetric filament discharge mode was observed with 983% and 221% increase in electron excitation temperature and density respectively. In the symmetrical filamentous discharge mode, the electron excitation temperature decreases rapidly by up to 79%, while the electron density remains in dynamic equilibrium. In addition, the electron excitation temperature decreases with the increase of helium flow, and the electron density maintains dynamic equilibrium with the increase of the flow rate. It is found that the input voltage control can realize the conversion between plasma discharge modes, and the helium flow rate can independently regulate the electron excitation temperature, providing a dual-dimensional collaborative control mode for optimizing the parameters of atmospheric pressure plasma in material preparation, modification, and biomedical applications.
Key words：Emission spectroscopy; Helium dielectric barrier discharge; Electron excitation temperature; Electron density
