Study On The Spatiotemporal Nonlinear Morphology Of The Pulsed Dc And Pulsed Microwave Discharges At Atmospheric Gas Pressure

In recent years,the technology of producing plasma under atmospheric pressure has become a research hotspot.It has the characteristics of low temperature,mild discharge,high active ion density,and no vacuum condition,and can be applied to biomedical and industrial material surface treatment.There are complex and variable spatiotemporal nonlinear behaviors in the discharge process of plasma generation,but such nonlinear phenomena have not been understood in pulsed DC and pulsed microwave discharge.In this paper,the spatiotemporal nonlinearity of pulsed DC arc discharge and pulsed microwave discharge is mainly studied.The specific research contents are as follows:(1)The complex spatial-temporal nonlinear behavior and formation mechanism of atmospheric low-power pulsed DC discharge plasma jet were studied.A pulsed DC arc discharge cold plasma jet is realized by constructing an electric arc discharger.A high-speed camera was used to observe the discharge morphology of the plasma jet.Using the control variable method,the effects of the distribution of active particles in different discharge regions and different pulse frequencies on the discharge effect were investigated.The results show that the temporal and spatial variation of the pulsed DC arc discharge channel is irregular,which shows the spatio-temporal nonlinear evolution behavior of the discharge channel.(2)The complex spatial-temporal nonlinear behavior and formation mechanism of atmospheric low-power pulsed microwave discharge plasma jet were studied.In this paper,a microwave resonance discharge device is constructed by using the method of resonance coupling discharge in which the plasma interacts with the microwave field.In the experiment,the argon plasma jet was generated by pulsed microwave discharge,and the bifurcation and chaos phenomena in time and space were observed for the first time.In the process of discharge,with the increase of microwave frequency,three typical forms,namely normal state,quasi-chaotic state and chaotic state,appear when the microwave frequency is modulated by 10 k Hz,30 k Hz and 60 k Hz.At the same time,the fluctuation of the input/reflection power on the oscilloscope was observed,and the input/reflection power map was drawn,which verified its nonlinear behavior in space and time.The high-speed images of three discharge modes were taken with ICCD camera,and the discharge morphologies were observed as three typical spatio-temporal nonlinear characteristics.According to the jet configuration of discharge mode,the electromagnetic simulation model is constructed,the electromagnetic simulation is run,and the electromagnetic spatial and temporal distribution is obtained.Combined with the experimental results and electromagnetic simulation,it is proved that the ionizing wave theory and the resonant discharge mode are the formation mechanism of the space-time nonlinear morphology of the pulsed microwave argon plasma jet.