High-frequency electron drift instability in the cross-field configuration of Hall thrusters

Abstract

A systematic study of a high-frequency electron drift instability is presented. It has very large wave numbers corresponding to wavelengths close to the electron gyroradius. The three-dimensional dispersion relation is derived for a model of a crossed electric and magnetic field configuration existing in the Hall thruster. It is shown that the instability develops in packets of oblique unstable modes perpendicular to the magnetic field. The evolution of the instability is also studied for distorted electron distribution functions obtained in particle-in-cell simulations.

Anomalous conductivity in Hall thrusters: Effects of the non-linear coupling of the electron-cyclotron drift instability with secondary electron emission of the walls

“…For very small values of k x , one observes the comb-like structure of the modes that was published in Ref. 20. For larger values of k x , this structure becomes continuous and the growth rate is somewhat reduced.…”

Dispersion relations of electron density fluctuations in a Hall thruster plasma, observed by collective light scattering

“…5,6 Unstable branches of the dispersion relation were found near discrete values of the perpendicular wave number k, each corresponding to an integer value of k cD . For each of these k-values, the unstable frequencies were expected in the 1-10 MHz range, with a very large group velocity.…”

“…This frequency range is close to that of the unstable modes that are expected in such an E ជ ϫ B ជ configuration, either from the fluid theory ͑the modified two-stream instability 20 ͒ or from kinetic theory. 6 This expected mode propagates in the direction of the E ជ ϫ B ជ drift. It is thus natural to attribute the large amplitude peak to fluctuations situated in the 9 o'clock side of the thruster channel.…”

“…Full two-dimensional PIC simulations have been performed 5 and analyzed in the frame of kinetic theory. 6 An unstable propagating electrostatic mode has been found to develop to a high-amplitude, nonlinear regime. This mode propagates a fluctuating electric field that is aligned with the E ជ ϫ B ជ direction, as is the wave vector k ជ .…”

Device convolution effects on the collective scattering signal of the E × B mode from Hall thruster experiments: 2D dispersion relation

“…It may be due to wall conductivity 7,12 or to micro-turbulence. 1,6,10,18 Micro-turbulence at the millimeter scale has been observed in PIC code simulations, 1,3 predicted by linear kinetic theory 5 and observed experimentally by the collective light scattering technique. 16,17 The collective light scattering technique, used together with a superheterodyne demodulation device, makes it possible to measure the spatial Fourier transform of electron density fluctuations.…”