A novel optical emission spectroscopy method for diagnostics of contribution of different ionization mechanisms and flux of ions in different valences in discharge channel of a Hall thruster

Abstract

The mass application of Hall thrusters poses the need for a diagnostic method of ionization mechanism in the discharge channel to boost the iteration and optimization of thruster design. This work presents an Optical Emission Spectroscopy (OES) method for diagnostics of the contribution of different ionization mechanisms and the flux of ions in different valences in the discharge channel of a Hall thruster. The emission spectra in the discharge channel are analyzed by jointly utilizing a collisional-radiative model, an ionization-excitation model, and a flux-conservation model. It is found that the intensities of some spectral lines can be converted into the reaction rates of collision processes, e.g., electron-induced excitation and ionization processes. The latter can further be used to determine the evolutions of particle fluxes by utilizing the conservation law of matter. The novel method is demonstrated on a kilo-watt Hall thruster. The evolutions of several parameters are determined using this method along the discharge channel, including the ionization rates of different mechanisms, particle fluxes, particle densities, and particle velocities. This novel method can be further developed by being jointly utilized with spectral imaging and tomography techniques, enabling diagnostics of multi-dimensional distributions of the above-mentioned parameters in the discharge channel and near-field plume.