Hall thruster plasma fluctuations identified as the E×B electron drift instability: Modeling and fitting on experimental data

Abstract

Microturbulence has been implicated in anomalous transport at the exit of the Hall thruster, and recent simulations have shown the presence of an azimuthal wave which is believed to contribute to the electron axial mobility. In this paper, the 3D dispersion relation of this E Â B electron drift instability is numerically solved. The mode is found to resemble an ion acoustic mode for low values of the magnetic field, as long as a non-vanishing component of the wave vector along the magnetic field is considered, and as long as the drift velocity is small compared to the electron thermal velocity. In these conditions, an analytical model of the dispersion relation for the instability is obtained and is shown to adequately describe the mode obtained numerically. This model is then fitted on the experimental dispersion relation obtained from the plasma of a Hall thruster by the collective light scattering diagnostic. The observed frequency-wave vector dependences are found to be similar to the dispersion relation of linear theory, and the fit provides a non-invasive measurement of the electron temperature and density. V C 2013 AIP Publishing LLC.

Rotating structures in low temperature magnetized plasmas—insight from particle simulations

“…Since one of the purposes of this paper is to illustrate how PIC MCC simulation can help identify and understand instabilities in E × B devices, we focus below on a particular micro-turbulence in the mm scale that has been predicted by PIC MCC simulations [40][41][42]73], observed by collective scattering experiments [28,42,[82][83][84] and leads to an increase of electron conductivity consistent with the measurements. This instability is termed as "electron-cyclotron drift instability" and results from the resonant coupling between Bernstein electron modes and ion acoustic waves.…”

Evolution of the electron cyclotron drift instability in two-dimensions

“…The general behavior of the growth rate of the instability is shown for several values of the k z parameter in We solve the dispersion relation numerically in Python 27 using the technique described in Ref. 20, where the solution is obtained through fixed point iteration using the relative error as a stopping condition. We use the convergence condition that |1 − ω i+1 /ω i | < 10 −6 for i ≥ 15.…”

“…2D axial-azimuthal simulations [14][15][16] , and 2D radialazimuthal simulations [17][18][19] . Many of these works focused on the possibility that ECDI simply becomes the ion sound instability analogous to the case of unmagnetized plasma 13,20 . We have shown in our previous nonlinear simulations that the transition to ion sound (which for the 1D case is only possible due to nonlinear diffusion in the short wavelength regime) does not occur 21 and the instability is driven by the dominant m = 1 cyclotron resonance.…”

Modulated Electron Cyclotron Drift Instability in a High-Power Pulsed Magnetron Discharge

“…Based on the parameters typical for experiments described in this Letter (electric field magnitude « 1 04 V /m , magnetic field magnitude of 8.8 mT at the measurement position), excited modes in the magnetron plasma are expected at wave number values which correspond to length scales on the order of a millimeter and below. However, the expected cyclotron resonances can be smoothed, result ing in an observed mode dispersion relation which is nondiscrete [9], To rapidly illustrate this, linear kinetic theory results for typical magnetron parameters (given in the figure caption) for an argon plasma are shown in propagation) smoothes the resonances. The resulting dispersion relation is linear and the corresponding mode group velocity is 2.5 km/s.…”