Investigation Of The Cold Atmospheric Pressure Plasma Jet

Cold atmospheric pressure plasma jet is a new type of plasma technology in recent years. The plasma generated in the discharge area can be ejected from the nozzle, and then forms directed flows and a further discharge in the surrounding air. The jet has many advantages such as low temperature, high concentrations of active particles, simple device and easier operation. There are broad prospects in the field of environmental protection, material modification, as well as biomedical engineering. So the jet is studied widely by domestic and foreign scholars. In this paper, Ne jet and Ar jet driven by sinusoidal voltages are chosen as the studying objects. Various optical and electrical detective techniques are used to study the fundamental features, the manipulations and the applications of the jets.Firstly, length, temperature, spectrum and discharge waveforms of the jets are studied. Jet length increases with the voltage increasing. While the voltage increases further, jet length increases slowly or even becomes shorter, due to the influence of air and the disturbance of discharge. Jet temperature is close to the room temperature and the electron excited temperature is less than 1.5×104K. Moreover, both of them rise with the voltage increasing. The spectrum contains the spectral lines of the working gas and the spectral lines of air. The relative intensities of the spectrum are different when the discharge stages or the locations are different. According to the mole fraction distribution of the working gas, the images of plasma jets and the variations of spectrum, the interactions between the directed noble gas column and the air are investigated. The results indicate that both the different decay rates of Ar spectral intensity and the generation, the decrease of OH radicals in spectrum are related to the air involved in the discharge. The jet driven by sinusoidal high voltage is a kind of multi-pulses discharge, and also there are no differences between the positive and the negative half periods.Secondly, the influences of modulating pulses to the plasma jet are also studied. The jet length changes little when the modulating pulse is used. The intensity of the reactive particles increases linearly with the modulating duty ratio. While for the modulating frequency, there are some differences between Ar jet and Ne jet. The modulating pulse, especially the modulating duty ratio, can linearly manipulate the number of reactive particles in the plasma jet without changing the jet length, which is helpful to the controlled applications of the plasma jet.Finally, some experiments related to the applications are studied with the plasma jet. The results show that the surface of material can become more hydrophilic with the jet processing and there are different optimal processing times for different materials and different processing positions in the jet.