Investigation of Hall effect thruster instabilities with axial-azimuthal PIC simulation using a collective Thomson scattering approach

The last decade witnessed a growing interest in Hall Effect Thrusters due to their efficiency. However, a full grasp of their operation is not yet available and one significant question remains to be the electron transport. Recent PIC simulations suggested that electron transport is strongly affected by small-scale fluctuations which can be investigated using Collective Thomson Scattering (CTS).

This work tries to benefit from the wave vector selectivity of the CTS and the resolution of the PIC results to investigate these fluctuations. This is achieved by analyzing the signal that a CTS virtual diagnostic observes from PIC. The PIC data are from a simplified benchmark by T.Charoy et al., where both the radial magnetic field and the ionization profile are fixed so that to remove the breathing mode oscillation. The collective scattering signal is calculated from the electron density maps using the expression of the scattered field.

An analysis along the channel axis highlights changes in the direction and intensity of the propagating modes between the ionization and the acceleration zones. An azimuthal dominant mode at k = 3 rad.mm-1 is enhanced throughout the channel while modes at larger k are damped. The dispersion relations are also computed as well as the fluctuation rate.