Stationary axial model of the Hall thruster plasma discharge: electron azimuthal inertia and far plume effects

Abstract

One-dimensional axial models of the plasma discharge of a Hall thruster provide a valuable picture of its physical behavior with a small computational effort. Therefore, they are very suitable for quick parametric analyses or as a support tool for analyzing the impact of modelling decisions. This paper extends a well-known drift-diffusion stationary, quasineutral model by adding electron azimuthal inertia (EAI), a nonzero thickness cathode layer, and the far-plume region where electrons demagnetize and cool down. The EAI dominates on the far plume and affects positively to thrust. For a small ion backstreaming current, EAI modifes much the electron velocities and density near the anode, but has no discernible effect on the electron cross-field transport. Electron axial inertia and azimuthal gyrovisosity are estimated. The thick cathode layer connects quasineutrally the near and far plumes but the coupling between these two regions is weak. The far plume region is sensitive to the decay length of the magnetic field, the downstream boundary conditions on the electron currents, and the stray electric currents.

Non-Maxwellian electron effects on the macroscopic response of a Hall thruster discharge from an axial–radial kinetic model

“…The relevance of the derivatives of M rθe and M zθe in the electron azimuthal equation are known as FLR effects. The contribution of M zθe (both as inertia and as gyroviscosity) near the anode has been observed previously in simulations with 1Dz fluid [35], 1Dz PIC [24] and 2Dzθ PIC [34] models. Parametric studies [35,46] show that these contributions near the anode are favored by large values of the locally Hall parameter and become nonmarginal only when the local electron density decreases much, thus locally increasing the electron drift velocities.…”

“…The contribution of M zθe (both as inertia and as gyroviscosity) near the anode has been observed previously in simulations with 1Dz fluid [35], 1Dz PIC [24] and 2Dzθ PIC [34] models. Parametric studies [35,46] show that these contributions near the anode are favored by large values of the locally Hall parameter and become nonmarginal only when the local electron density decreases much, thus locally increasing the electron drift velocities. Therefore, on the one hand, these effects require a good assessment of both electron-neutral collisionality and anomalous diffusion neat the anode.…”

“…The analysis of electron macroscopic response will reveal that pressure tensor and heat flux present complex behaviors, already identified in our 1Dr PIC model. Additionally, FLR effects will be found to become relevant near the anode; as in previous 1Dz fluid [35], 1Dz PIC [24] and 2Dzθ PIC [34] models.…”

“…Interestingly, near the anode, u θe ≈ c e . Different works on 1D fluid models by Ahedo and co-workers [35,45,46] have demonstrated that (1) the electron azimuthal inertia matters near the anode for…”

A non-neutral 1D fluid model of hall thruster discharges: full electron inertia and anode sheath reversal

“…The major difference between the quasi-neutral model used in this work with respect to the one presented in [12], is the absence of the volumetric cathode and far plume, which is here substituted by a planar cathode. While the far plume has little influence on the discharge properties inside the channel, it was observed by Bello-Benítez and Ahedo [25] how the thickness of the volumetric cathode can mildly modify the stationary plasma discharge around the cathode region and surprisingly in the proximity of the anode. However, the volumetric source term has non-negligible effects on the thruster dynamics, as highlighted in figure 11, where the occurrence of breathing mode at 10 ms is evaluated for different thicknesses of the volumetric source term.…”