Unraveling the Influence of Non-Maxwellian Electron Energy Distribution on Argon Inductively Coupled Plasma

The objective of this work is to develop a self-consistent model for an inductively coupled radio frequency argon plasma. Inductively coupled plasma (ICP) torches are known to exhibit a high degree of non-equilibrium at low and moderate pressures, resulting in situations where the electron temperature is significantly higher than the gas temperature. This leads to a substantial deviation of the electron energy distribution function (EEDF) from the Maxwellian form and a drastic change in the electron coefficients. To accurately simulate this non-equilibrium behavior in fluid model simulations, the variation in the electron coefficients needs to be considered, which can be determined by solving the electron Boltzmann equation (BE) using collision cross-sections. In this work, the in-house magneto-hydrodynamic model is coupled with a BE solver to investigate the degree of departure from local thermodynamic equilibrium. A step-by-step approach is adopted, starting with 0D cases and comparing results between our in-house codes coupled with the Boltzmann solver and another software called ZDPlasKin. Once verified, the next step involves coupling our in-house 1D CFD solver with the Boltzmann solver, showing good agreement in the results. The common factor in all test cases is the presence of conditions leading to a high degree of ionization. The subsequent simulations will focus on the conditions of the CHESS plasmatron exhibiting low ionization degrees. Additionally, future work aims to enrich the chemistry model for a more realistic representation of the ongoing chemical processes in highly non-equilibrium conditions of ICPs.