Temperature dependence of pattern transitions on water surface in contact with DC microplasmas

Abstract

The DC-driven atmospheric-pressure microplasma is generated in a helium gas flowing through the metal tube cathode and is brought into contact with the surface of the water with the immersed Pt anode. By adjusting the gas flow, discharge current and gap distance, self-organized patterns are observed and varied sequentially from the homogeneous spot to the ring-like shape, distinct spot shape and the gearwheel shape on the water surface. The electrode temperature is measured and the gas temperature of the plasma discharge is calculated through the numerical fitting of the second positive system of the spectrum of N 2 molecules. It is shown that the pattern transition is related to the electrode and gas temperatures of the plasma. Moreover, specific discretization features of the patterns are shown to appear at certain gas temperatures.

Numerical studies on the influences of gas temperature on atmospheric-pressure helium dielectric barrier discharge characteristics

“…The evolution of the averaged electron density shows that an atmospheric-pressure helium DBD can transit from the discharge column (or ring plasma discharge) at some local locations to a homogeneous discharge in the whole gas gap only by increasing the gas temperature. Some experimental results also show that a helium DBD can operate in different discharge modes, such as a homogeneous spot or the ring-like shape, by varying the gas temperature [11,35,36]. It is also worth noting that the evolution of an atmospheric-pressure helium DBD with the gas temperature is very similar to that of an atmospheric-pressure argon DBD with the applied voltage [17].…”

Various concentric-ring patterns formed in a water-anode glow discharge operated at atmospheric pressure

“…T g also increases with increasing current. As is well known [22], T g has a decisive effect on the pattern structure. Therefore, the concentric-ring pattern transits concurrently with T g variation.…”

“…Diameter of the single ring increases until reaching a maximum, and then decreases with the increase of discharge current [18]. Besides, the single-ring pattern varies and may transit to other discharge patterns with adjusting gas flow rate, discharge current, and gap width [22]. Although various parameters can affect pattern transitions, the determining factor is related to electrode and gas temperatures [22].…”

“…Besides, the single-ring pattern varies and may transit to other discharge patterns with adjusting gas flow rate, discharge current, and gap width [22]. Although various parameters can affect pattern transitions, the determining factor is related to electrode and gas temperatures [22]. In fact, the formation mechanism of pattern is still not understood very well [23].…”

Self‐organized pattern formation and plasma diagnosis in atmospheric pressure helium glow discharges with a liquid anode

“…In addition, because the composition of the discharge body in an open environment severely impacts electron mobility, an essential parameter in the current–voltage method, this method is not suitable for diagnosing the density of plasma in open air. Based on previous studies, [ 28,29 ] it is feasible to diagnose the electron density of plasma when SOPs are formed on a liquid anode. The gas temperature $$\,{T}_{g}$$ is estimated by calculating the rotational temperature $${T}_{\mathrm{rot}}$$ of the plasma.…”