The effect of alternative propellants on the electron drift instability in Hall-effect thrusters: Insight from 2D particle-in-cell simulations

Abstract

Hall-effect thrusters (HETs) operated with xenon are one of the most commonly used electric propulsion technologies for a wide range of space missions, including drag compensation in low Earth orbit, stationkeeping, and orbital insertion, as access to space becomes more affordable. Although anomalous electron transport, the electron drift instability (EDI), and secondary electron emission (SEE) have been studied experimentally and numerically in xenon-based HETs, the impact of alternative propellants is still poorly characterized. In this work, a two-dimensional particle-in-cell/Monte Carlo collision (PIC/MCC) code is used to model the (r − θ) plane of a HET operated separately with four different noble gases: xenon, krypton, argon, and helium. Models for electron induced secondary electron emission (SEE) and dielectric walls are implemented in order to investigate the coupling between the propellant choice and the radial thruster walls. For all conditions and propellants studied, an EDI and enhanced electron cross-field transport are observed. The frequency of the instability, as well as the electron mobility, are compared with analytical expressions from a recently developed kinetic theory. Confirming this theory, it is shown that while the frequency of the EDI depends on the propellant mass, the electron mobility appears to be almost independent of the propellant choice.

2D axial-azimuthal particle-in-cell benchmark for low-temperature partially magnetized plasmas

“…The code is parallelized via MPI through a domain decomposition. It has been verified with the 1D helium benchmark of Turner et al [19] (further details in [28,29]) and extensively used to simulate the radial-azimuthal plane of a Hall Thruster [28,30,31]. For this benchmark, the code was adapted to the axial-azimuthal plane and accelerated via a load-balancing algorithm (adjusting periodically the size of each processor domain to have approximately the same number of particles inside each processor).…”

Physics of E × B discharges relevant to plasma propulsion and similar technologies

“…Various values of the effective z k were reported in different simulations [195], [193], [194], [24]. Effects of Secondary Electron Emission (SEE) and different propellants were studied [194], [24] and it was shown that the EDI activity is affected by the reduced electron temperature due to sheath cooling. Besides, SEE induces large electron transport due to near-wall effects.…”

“…The important role of the modified two-stream instability, due to a finite z k , leading to strongly anisotropic heating and large scale radial structures in the anomalous current, was emphasized [195]. Various values of the effective z k were reported in different simulations [195], [193], [194], [24]. Effects of Secondary Electron Emission (SEE) and different propellants were studied [194], [24] and it was shown that the EDI activity is affected by the reduced electron temperature due to sheath cooling.…”

Nonlinear regimes of the electron cyclotron drift instability in Vlasov simulations

“…, where n e and Ẽ are the electron density and the self-consistent electric field and are calculated as for unmagnetized ion-sound turbulence. These results were validated against some particle-in-cell (PIC) simulations [18][19][20] .…”