Self-consistent global plasma model with application to a Microwave Electrothermal Thruster with atomic propellants

Global (0D) plasma models are a subclass of fluid models that compute volume-averaged quantities (i.e., densities and temperature) by solving a set of particle and power balance equations. They are extremely useful for investigating how relevant parameters affect the plasma chemistry and the power deposition, without the computational resources and time required by spatially resolved models. Consequently, they can be exploited to study plasma discharges for processing applications, with also growing interest by the fusion and electric propulsion communities in the recent years. This study aims at developing a global plasma model which compute the plasma parameters and the reactor wall temperature self-consistently, by solving a set of balance equation describing the evolution of the plasma species, the electron and heavy species temperature, and the wall temperature. The model has been tested on an electric thruster known as the Microwave Electrothermal Thruster (MET), using argon and helium as propellants, exploring an input power range of $1-5\,kW$ and chamber radii within $50-77\,mm$, while maintaining the resonant frequency at $2.45\,GHz$. Simulation results demonstrates the predictive capability of this novel model as well as its effectiveness in exploring a broad parameter space and identifying optimal operating conditions within reasonable computational times.