Microwave micro-discharges at atmospheric pressure: experiments and simulations

We present a microwave (2.45 GHz) source based on a planar transmission line configuration, which uses a continuous excitation (1-50 W) to produce stable micro-plasmas at atmospheric pressure in air, Ar and He (plasmas are produced within the 50-200 $\mu $m gap created between two metal electrodes). The source is studied using both experiments [1] and simulations [2]. Experiments (i) measure the return loss of the source (hence its quality factor); (ii) use OES diagnostics to obtain the plasma (ro-vibrational and excitation) temperatures and the electron density; and (iii) check the plasma expansion by resorting to an imagery analysis. Simulations (i) describe the electromagnetic behavior of the source using the numerical code CST {\textregistered} and an analytical transmission line model; and (ii) characterize the plasmas produced, using a 1D self-consistent stationary hybrid code for Ar, that solves the fluid-type transport equations coupled with the kinetic electron Boltzmann equation. The system exhibit power densities of 1-5 kW cm$^{-3}$ for electron densities of $\sim $10$^{13}$-10$^{14 }$cm$^{-3}$. [1] J. Greg\'{o}rio et al, these proceedings; [2] L.L. Alves et al, these proceedings.