Non-thermal atmospheric RF plasma in one-dimensional spherical coordinates

We present one-dimensional simulations of atmospheric pressure RF-excited plasma with two concentric spherical electrodes and the inner electrode powered. The coupled continuity equations and electron energy equation are solved with Poisson’s equation using the finite element method. A mode transition is observed in the discharge power-voltage curve between 1 mW and 1000 mW. In the low power mode, ionization rate peaks only near the inner electrode. In the high power mode, however, the rate of ionization peaks near the outer electrode as well. The ionization rate near the outer electrode is due to ohmic sheath oscillation heating of electrons. Electron heating near the outer electrode may have implications for surface processing in atmospheric pressure microdischarges.