A new 2D fluid-MC hybrid approach for simulating nonequilibrium atmospheric pressure plasmas: density distribution of atomic oxygen in radio-frequency plasma jets in He/O2 mixtures

Abstract

A spatially two dimensional fluid-MC hybrid (fluid-kinetic) simulation method is developed and applied to the COST reference microplasma jet operated in helium with an oxygen admixture of 0.5\%, excited by a single frequency voltage waveform with $f=13.56$~MHz and $V_{\rm rms}=275$~V. The simulation approach is based on a fluid model augmented by a Monte Carlo module that generates electron impact rates for the continuity equations solved by the fluid module. This method is capable of providing the same level of accuracy as PIC/MCC simulations with an agreement within 5-10\% at atmospheric pressure, while being significantly faster (with a speedup factor of 30 for serial to 50 for parallel implementation). The simulation results are compared to previous measurements of atomic oxygen densities (Steuer D et {\it al.} 2021 {\it J. Phys. D: Appl. Phys.} {\bf 54} 355204), and show a very good agreement. It is found that the buildup and saturation of the atomic oxygen density distribution along the jet are due to the interplay of chemical and electron impact reactions as well as of the gas flow. Comparing the simulation results to that of Liu Y et {\it al.} 2021 {\it J. Phys. D: Appl. Phys.} {\bf 54} 275204, it is inferred that fluid models where a 2-term BE solver is used, fail to describe the COST jet in an accurate manner due to the underestimation of the electron impact rates.