Kinetic Monte Carlo simulations of plasma-chemistry

The interest in nanosecond pulsed discharges has been rising quickly due to their strong non-equilibrium properties. The typical plasma-chemistry models based on the low-anisotropy and quasi-stationary approximations to the Electron Energy Distribution Function may fail to describe these discharges correctly, due to the high reduced electric fields (E/N) and very short timescales involved. These limitations can be overcome with a self-consistent and unified formulation based on Kinetic Monte Carlo (KMC) techniques. A simultaneous KMC description of the electron and heavy-species kinetics would enable a rigorous inclusion of the time-dependent influence of different excited states in the electron kinetics and vice-versa, and would not be limited to a restricted range of E/N.

As a first step to achieve such unified formulation, a KMC algorithm to solve gas-phase chemistry was implemented and validated in the thermodynamic limit. However, the densities of the minority species have considerable fluctuations. Two novel variance-reduction techniques to achieve an efficient and accurate time-evolution of all the species, including the minority ones, are proposed and successfully applied.