2D numerical simulation of capacitively coupled RF plasma shower device

Summary form only given. A capacitively coupled RF discharge at atmospheric pressure is studied by means of a time-dependent, two-dimensional fluid model. The plasma is created in a stationary argon gas flow between two multi-holes perforated electrodes, forming a shower [1]. The inner electrode is powered with a frequency of 13.56 MHz, the outer electrode is grounded. The model solves the mass balance equations for the relevant active species and the electron energy balance equation in conjunction with the Poisson equation for the field sustaining the plasma. The mass balance equations of the active species are calculated using the drift-diffusion-convection approach, thus taking the bulk velocity into account. The velocity field is calculated with the Navier-Stokes module of the Plasimo toolkit. Three different sub-studies were carried out in order to explore step-by-step the complex interplay between the geometry and the gas flow: a) a flowless classical parallel plates' geometry, b) a flowless perforated parallel plates' configuration and c) the plasma shower. Strongly non- Maxwellian kinetics is found and as a consequence the excited species are much more abundant than the charged particles. Molecular ions are the dominant ion species and it was found to unbalance even more the ion/metastable ratio via dissociative recombination to the metastable species making it the main active species in the plasma. The effect of the shower holes and the recirculation gas flow within the electrodes on the plasma is examined. The perforation of the electrode's plates modifies the spatial distributions of the E-field, leading to an intra-hole field augmentation and therefore to activation of these regions of the plasma. As the most effective outward transport mechanism, the gas flow is the basis of the formation of the post-discharge region. In addition to modifying the distribution of the plasma particles in the spatial afterglow, the flow recirculation reduces the wall losses and facilitates the ionization and excitation processes in between the plates. Thus it plays a key-role in the stabilization of the discharge.