Two-dimensional effects on electrostatic instabilities in Hall thrusters. I. Insights from particle-in-cell simulations and two-point power spectral density reconstruction techniques

Petronio, Federico; Charoy, Thomas; Laguna, Alejandro Alvarez; Bourdon, Anne; Chabert, Pascal

doi:10.1063/5.0119253

Cited by 8 publications

(3 citation statements)

References 50 publications

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“…The neutrals' dynamics in the axial-azimuthal simulations is resolved in terms of their density and velocity evolution by solving a 1D axial Euler system of fluid equations. The adoption of a fluid description for the neutrals is in line with the current practices being pursued by the community for the axialazimuthal simulations [20,31]. The details of our neutrals' fluid solver, its benchmark results, and its application in 1D axial and quasi-2D axial-azimuthal simulations of a SPT100type Hall thruster domain can be found in [32].…”

Section: Simulations' Setup and Conditionsmentioning

confidence: 90%

Reduced-order particle-in-cell simulations of a high-power magnetically shielded Hall thruster

Reza

Farbod

Knoll

et al. 2023

Plasma Sources Sci. Technol.

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High-power magnetically shielded Hall thrusters have emerged in recent years to meet the needs of the next-generation on-orbit servicing and exploration missions. Even though a few such thrusters are currently undergoing their late-stage development and qualification campaigns, many unanswered questions yet exist concerning the behavior and evolution of the plasma in these large-size thrusters that feature an unconventional magnetic field topology. Noting the complex, multi-dimensional nature of plasma processes in Hall thrusters, high-fidelity particle-in-cell (PIC) simulations are optimal tools to study the intricate plasma behavior. Nonetheless, the significant computational cost of traditional multi-dimensional PIC schemes renders simulating the high-power thrusters without any physics-altering speed-up factors unfeasible. The novel reduced-order “quasi-2D” PIC scheme enables a significant reduction in the computational cost requirement of the PIC simulations. Thus, in this article, we demonstrate the applicability of the reduced-order PIC for a cost-efficient, self-consistent study of the physics in high-power Hall thrusters by performing simulations of a 20 kW-class magnetically shielded Hall thruster along the axial-azimuthal and radial-azimuthal coordinates. The axial-azimuthal quasi-2D simulations are performed for three operating conditions in a rather simplified representation of the thruster’s inherently 3D configuration. Nevertheless, we have resolved self-consistently an unprecedented 650 µs of the discharge evolution without any ad-hoc electron mobility model, capturing several breathing cycles and approximating the experimental performance parameters with an accuracy of 70 to 80 % across the operating conditions. The radial-azimuthal simulations, carried out at three cross-sections corresponding to different axial locations within the discharge channel, have casted further light on the evolution of the azimuthal instabilities and the resulting variations in the electrons’ cross-field mobility and the plasma-wall interactions. Particularly, we observed the development of a long-wavelength, relatively low-frequency wave mode near the exit plane of the thruster’s channel that induces a notable electron transport and a significant ion heating.

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Section: Simulations' Setup and Conditionsmentioning

confidence: 90%

Reduced-order particle-in-cell simulations of a high-power magnetically shielded Hall thruster

Reza

Farbod

Knoll

et al. 2023

Plasma Sources Sci. Technol.

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show abstract

“…Referring to Eqs. ( 8)- (10), it becomes evident that change in electron temperature directly influences variation in R ie , subsequently leading to the variation of axial electron mobility. As depicted on the vertical axis of Fig.…”

Section: Effect Of Edi On Axial Electron Mobilitymentioning

confidence: 99%

“…The majority of studies have used PIC simulation that contains azimuthal direction to simulate these oscillations. These models include one-dimensional (1D) azimuthal direction, [5][6][7] two-dimensional (2D) axial-azimuthal directions, [8][9][10][11][12] 2D radial-azimuthal directions, [13][14][15][16] and three-dimensional (3D) full-channel [17,18] numerical simulations. Ducrocq et al [19] investigated the development of EDI and suggested that when the electric drift velocity is smaller than the electron thermal velocity, the EDI fluctuations satisfy an ion-sound wave dispersion relation and the saturation of the EDI may be related to ion Landau damping.…”

Section: Introductionmentioning

confidence: 99%

Growth mechanism and characteristics of electron drift instability in Hall thruster with different propellant types

Chen 陈,

Kan 阚,

Gao 高

et al. 2024

Chinese Phys. B

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The existence of a significant electron drift instability (EDI) in the Hall thruster is considered one of the possible causes of the abnormal increase in axial electron mobility near the outlet of the channel. In recent years, extensive simulation studies have been conducted to investigate the characteristics of EDI, but the excitation and growth mechanisms of EDI in both linear and nonlinear stages are unclear. In this work, a one-dimensional PIC model on the azimuthal direction of the thruster near-exit region is established to gain further insights into the mechanism of the EDI in detail, and the effects of different types of propellants on EDI characteristics are discussed. The changes in axial electron transport caused by EDI under different types of propellants and electromagnetic field strengths are also examined. The results indicate that EDI undergoes a short linear growth phase before transitioning to the nonlinear phase and finally reaching saturation through the ion Landau damping. EDI drives a significant ion heating in the azimuthal direction through electron-ion friction before entering the quasi-steady state which increases the axial mobility of the electrons. Applying propellants with lighter atomic weight can effectively suppress the oscillation amplitude of EDI, but increases the linear growth rate of EDI as well as the frequency and phase velocity. The axial electron mobility increased under the EDI by three orders of magnitude compared to the classical mobility, this simulated result obtained are consistent with experimental phenomena. The change in the type of propellant is not sufficient to significantly alter the electron axial mobility. It’s also found that collisions between electrons and neutral gases have a significant impact on electron axial mobility under the influence of EDI, increasing the strength of the electric field and decreasing the strength of the magnetic field both effectively suppress the axial transport of electrons.

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Two-dimensional effects on electrostatic instabilities in Hall thrusters. II. Comparison of particle-in-cell simulation results with linear theory dispersion relations

et al. 2023

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In Paper I, we successfully used an external circuit to significantly damp the Breathing Mode (BM) oscillations in 2D particle-in-cell self-consistent simulations of the axial–azimuthal plane of a Hall thruster. We also introduced the two-point power spectral density reconstruction method (PSD2P) used to analyze electrostatic instabilities and generate dispersion diagrams in azimuthal and axial directions, at various times during the BM period. Here, a 3D Dispersion Relation (DR) for electrostatic modes is calculated by linearizing the continuity/momentum fluid equations for electrons and ions. We show that by taking the appropriate limits, this relation can be simplified to derive the DRs of some well-known [Formula: see text] instabilities, such as the electron cyclotron drift instability and its evolution to the Ion Acoustic Wave (IAW), and the Ion Transit-Time Instability (ITTI). The PSD2P diagrams demonstrate the importance of considering the 2D nature of the IAW and ITTI, which have been previously considered to be mono-dimensional (azimuthal and axial, respectively). In particular, we show that the IAW grows near the maximum of the magnetic field and due to its axial components propagates toward both the anode and the cathode (in addition to the well-known azimuthal propagation). The resulting wavefront is, therefore, bent. By analogy to the propagation of acoustic waves in gases, it is proposed that the cause of the IAW wavefront bending is the strong electron temperature gradients in the axial direction. We also show that the ITTI has a strong positive growth rate when a small azimuthal component is present. Finally, we observe that the ITTI significantly affects the discharge current.

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Two-dimensional effects on electrostatic instabilities in Hall thrusters. I. Insights from particle-in-cell simulations and two-point power spectral density reconstruction techniques

Cited by 8 publications

References 50 publications

Reduced-order particle-in-cell simulations of a high-power magnetically shielded Hall thruster

Reduced-order particle-in-cell simulations of a high-power magnetically shielded Hall thruster

Growth mechanism and characteristics of electron drift instability in Hall thruster with different propellant types

Two-dimensional effects on electrostatic instabilities in Hall thrusters. II. Comparison of particle-in-cell simulation results with linear theory dispersion relations

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