Non-equilibrium Atmospheric Jet Microplasmas

The atmospheric jet microplasma is a micro non-linear and non-equilibrium plasma system.Microplasmas have received much attention in numerous applications because of creating a highly reactive environment.A deeper unstanding will lead to a better utilization of microplasma.This thesis study non-equilibrium characteristics of the atmospheric jet microplasma by experimental methods.The thesis includes four experiments.The first,a stable direct current atmospheric pressure normal glow discharges in ambient air were produced between the watersurface and the metallic capillary.The nitrogen rotational and vibriational temperatures are measured in parameters space constructed by the discharge current and helium gas flux.Vibrational temperature is positively correlated with gas flux and negatively correlated with discharge current.On the contrary,rotational temperature is negatively correlated with gas flux and positively correlated with discharge current.It is found that the vibrational degree of the nitrogen molecule has priority to gain energy than the rotational degree of nitrogen molecule in nonequilibrium helium microplasma.The second experiment is designed to explore the two dimensional temperature maps of the atmospheric argon discharge consisting of pin-to-plane electrodes supplied by a high voltage DC source.The two dimensional image plane focused by a quartz lens was scanned by the fiber probe driven by a 3D Mobile Platform.The rotational and vibrational temperatures are calculated using nitrogen emissions collected by the high resolution spectrometer and high sensitive intensified charge coupled device(ICCD).The rotational temperature varies from 1558.15 K to 2621.14 K and vibrational temperature varies from 3010.38 K to 3774.69 K,indicating a great temperature gradient due to small discharge size.The temperature maps show a lateral expansion and a sharp truncation in the radial direction.A double layers discharge is identified.The third experiment studied the macro evolution of the micro atmospheric glow discharge generated between a micro argon jet into ambient air and static water.Non-linear behaviors are found for the micro discharge when the water acts as a cathode,different from the discharge when water behaves as an anode.Motions of the water surface at different discharge currents show that the water surface lowers increasingly rapidly when the water acts as a cathode.In contrast,the water surface lowers at a constant speed when the water behaves as an anode.The light curves are similar to logistic growth curves,suggesting that a self-inhibition process occurs in the micro discharge.Meanwhile,the total brightness increases linearly during the same time when the water acts as an anode.Discharge-water interactions cause the micro discharge to evolve.The charged particle bomb process is probably responsible for the different behavior of the micro discharges when the water acts as cathode and anode.At last,we reported on the experimental observation of three dimensional self-deformation in an atmospheric micro discharge of the helium microjet through a tube into the ambient air upon a water electrode.The geometry of the discharge system is axial symmetric.While decreasing the discharge current,three dimensional collective motion of plasma filaments are directly observed.The three dimensional configuration of the discharge self changed from an axial symmetrical horn to a rectangular horn when the water acts as a cathode.