Charged-particle transport models for global models

Abstract

This work analyses the influence of different charged-particle transport models on the global modeling of low-temperature plasmas. The simulations use the LisbOn KInetics (LoKI) simulation tool, calculating the charged-particle loss frequency due to transport with various formulations, categorized into two large groups: ambipolar-based and h-factor transport models. The models are applied to the description of (i) a DC discharge in oxygen (as example of an electronegative multi-ion plasma), at low to intermediate pressures, adopting a validated kinetic scheme as reference model; (ii) a microwave discharge in helium (as example of an electropositive multi-ion plasma), from low to atmospheric pressures, proposing and validating an updated kinetic scheme that bridges two previous models, adjusted separately for low to intermediate pressures and for atmospheric pressure. The analysis shows that using different charged-particle transport models can result in uncertainties of 20-60% and 8-115% in the discharge characteristics of oxygen and helium, respectively, with larger dispersion at low pressure and low electron density. The spreading in the results is observed also in the densities of the main plasma species, corresponding to uncertainties up to 60% and within 50-150% in oxygen and helium, respectively. Since transport accounts for more than 50% of total charge losses, this mechanism should always be part of the quantitative sensitivity analysis of a kinetic scheme, considering several models with different validity domains, according to the electro-positive/negative single-/multi-ion plasma under study and the low/high pressure conditions considered.