3D Particle-in-Cell simulation of the impact of the Modified Two Stream Instability in Hall thrusters

Kinetic instabilities like the electron cyclotron drift instability (ECDI) and modified two-stream instability (MTSI) significantly influence electron transport in Hall thrusters (HT) by driving anomalous cross-field mobility through wave-induced electron scattering [1,2]. This study presents a three-dimensional (3D) particle-in-cell (PIC) investigation of the MTSI, analyzing its nonlinear development and coupling with the ECDI. Modeling the MTSI growth requires the inclusion of the radial direction and hence the model must be 3D. The algorithm has a couple of simplifying assumptions to speed-up the calculation and pinpoints the mechanisms leading to the formation of the instabilities: the electron transport is decoupled from ionization (a fixed source term), neutral dynamics and collisions are not implemented. The simulation domain includes a section of the canal (i.e, with dielectric surfaces in the radial direction) and the plume. We observe that the MTSI grows progressively stronger with increasing magnetic field strength (from a peak value of 100G to 200G), resulting in significant changes to electron transport in the Hall thruster (HT). In addition, the ECDI wave pattern becomes strongly perturbed by its coupling with the MTSI.