Perturbation analysis of ionization oscillations in Hall effect thrusters

TLDR

The study presents a perturbation analysis of ionization oscillations in Hall effect thrusters, incorporating the electron energy equation alongside heavy-species transport. The authors employ linear perturbation equations of the discharge plasma, incorporating the electron energy equation and heavy-species transport, to analyze excitation, stabilization, and the effects of electron energy loss mechanisms such as wall heat loss, inelastic collisions, and convective heat flux. The ionization instability appears only when electron energy perturbations are considered, and it can be damped by reducing electron transport and increasing electron temperature, which enhances wall energy loss and neutral atom flow damping.

Abstract

A perturbation analysis of ionization oscillations, which cause low frequency oscillations of the discharge plasma, in Hall effect thrusters is presented including the electron energy equation in addition to heavy-species transport. Excitation and stabilization of such oscillations, often called the breathing mode, are discussed in terms of the growth rate obtained from the linear perturbation equations of the discharge plasma. The instability induced from the ionization occurs only when the perturbation in the electron energy is included while the neutral atom flow contributes to the damping of the oscillation. Effects of the electron energy loss mechanisms such as wall heat loss, inelastic collisions, and convective heat flux are discussed. It is shown that the ionization oscillations can be damped when the electron transport is reduced and the electron temperature increases so that the energy loss to the wall stabilizes the ionization instability.