Study of the collisional effects on kinetic instabilities in Hall thruster devices

Electron-neutral collisions play an important role in the physics of Hall thrusters, providing the necessary ionization crucial for thrust generation. In this work, we have analyzed the effect of electron-neutral collisions on the high-frequency instabilities in Hall thruster plasmas. Numerical studies of Hall thruster plasmas have shown enhanced anomalous transport and rapid radial heating due to high-frequency oscillations driven by the Electron Cyclotron Drift Instability (ECDI) and Modified Two-Stream Instability (MTSI). Although numerical simulations demonstrate these instabilities, the complex nonlinear interactions associated with these instabilities and the effect of collisions on these instabilities are yet to be understood completely. In this work, we present the results of our computational studies on the effect of collisions on ECDI/MTSI using an in-house 2D particle-in-cell-Monte Carlo Collision code, primarily focusing on the spectral behavior of these instabilities. Our findings indicate that electron-neutral collisions certainly enhance the MTSI mode at the expense of the ECDI mode, causing an inverse-cascade to long wavelength modes. In addition, collisions enhance the mobility of electrons along the axial direction, accompanied by a stronger radial-azimuthal electron temperature anisotropy.