LAUSR

The present study investigates the physics of a nanosecond-pulsed microplasma operated at a pressure of 200 mbar with the help of a Particle-in-Cell simulation with Monte Carlo treatment of collision (PIC/MCC) and (semi-)analytical models. The discharge is ignited in a 1 mm gap between two parallel molybdenum electrodes by applying a voltage in the kV-range for several tens to hundreds of nanoseconds. A PIC/MCC simulation is developed in order to describe an experiment performed under identical conditions. Additionally, the simulation includes the external electrical circuit to perform ab-initio calculations of the complete experimental setup. Notable features of the PIC/MCC are (1) the adjustment of super-particle weights to reduce the computational load during drastic changes of the plasma density, which reaches values up to a few 10^19 m−3, and (2) the inclusion of dissociative recombination of the N4+ ions, which is the key loss process for the charge carriers in the plasma bulk regions. The current and voltage waveforms obtained from the simulation are compared to the experimentally measured ones and good agreement is found. After ignition, the discharge establishes a quasi-steady state exhibiting spatial features similar to a conventional DC glow discharge. Using the PIC/MCC results, reasonable approximations are identifeid, which allow the development of different analytical fluid models for the individual plasma regions. These models are able to reproduce the key features of the discharge in agreement with the PIC/MCC results. The simplified models for the different discharge regions can be combined to describe the global behaviour of the discharge and - in a next step - might be used to develop computationally efcifient global chemistry models that account for the different power dissipation mechanisms along the discharge gap.