Numerical simulations of radio frequency capacitively coupled atmospheric pressure micro plasma jets: from fluid to kinetic models*

Based on the COST-reference micro plasma jet, radio frequency capacitively coupled atmospheric pressure discharges operated in He/O₂ mixtures are investigated by numerical simulations, including a fluid dynamics model and a kinetic hybrid model. The simulation results are compared with various experimental measurements. The fluid model is performed by nonPDPSIM. It is shown that the fluid model is capable of capturing the electron heating mode transitions. The electron heating dynamics and reactive neutral species generations are enhanced in the trenches by using a structured electrode topology. In the kinetic hybrid model, electrons are traced by the Particle-in-cell/Monte Carlo Collision algorithm, while ions and neutral species are handled by fluid equations. The simulated results obtained from the hybrid model, show quantitative agreement with experimental results, including the electron impact excitation rates, the helium metastable density and the atomic oxygen density. The electron energy probability function is found to be spatio-temporally controlled by the voltage waveform tailoring. The simulation results from both models demonstrate that desired neutral species generations in a micro atmospheric pressure plasma jet can be enhanced and controlled via adjusting external discharge parameters, such as the shape of the voltage waveform, and the electrode structure.