Evidence of Counter-Streaming Ions near the Inner Pole of the HERMeS Hall Thruster

Huang, Wensheng; Kamhawi, Hani; Herman, Daniel A.

doi:10.2514/6.2019-3897

Cited by 7 publications

(1 citation statement)

References 18 publications

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“…High ion energies have also been inferred from laser-induced fluorescence (LIF) measurements of singly charged xenon ion velocities in the plume of the cathode in HERMeS thrusters. [34][35][36][37] The mean velocities correspond to energies of 15-30 eV, which are somewhat lower than most of the values measured in this experiment, with FWHM values of 21-42 eV, which are comparable to or larger than our measurements. Lopez Ortega postulated that azimuthal acceleration of ions in the cathode plume might produce high radial velocities.…”

Section: B Contributions Of Cathode Ions To Erosionsupporting

confidence: 59%

Use of an accelerated testing method to characterize inner front pole cover erosion in a high power Hall thruster

Polk

Lobbia

Barriault

et al. 2021

Journal of Applied Physics

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Erosion characteristics on the cover of the inner front pole in a 12.5 kW Hall thruster were measured over a wide range of operating conditions in tests of 6–14 h duration using an accelerated test method and a very sensitive, radioactive tracer-based erosion diagnostic. The operating points included the nominal 300–600 V conditions on a constant 20.8 A throttle curve and conditions at other currents spanning the throttling envelope and with varying magnetic field strength, facility pressure, and discharge voltage oscillation amplitude. Surprisingly, the results show that the highest wear rates occur at the lowest voltages and currents. The wear rates were insensitive to discharge voltage ripple but increased monotonically with magnetic field strength, particularly near the inner radius of the pole cover. The inner region was also sensitive to facility pressure, showing lower rates at a higher pressure level. Separate experiments in which the energy distributions of ions generated by the hollow cathode were measured suggest that the cathode plume may be a source of energetic ions responsible for some of the erosion trends, in addition to ions originating in the thruster plume.

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Section: B Contributions Of Cathode Ions To Erosionsupporting

confidence: 59%

Use of an accelerated testing method to characterize inner front pole cover erosion in a high power Hall thruster

Polk

Lobbia

Barriault

et al. 2021

Journal of Applied Physics

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Non-classical electron transport in the cathode plume of a Hall effect thruster

et al. 2020

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An experimental investigation is presented into the wave-driven electron transport in the near-field plume of a hollow cathode operating in a 300 V, 4.5 kW magnetically shielded Hall thruster. Correlational analysis of probe measurements in the cathode plume shows two types of electrostatic waves: ion acoustic turbulence propagating along the applied longitudinal magnetic field at frequencies from 500 to 1250 kHz and coherent, azimuthal anti-drift waves with a fundamental frequency of 95 kHz and mode numbers from m=1−4. A quasilinear analysis is applied to quantify the impact of each wave on the electron transport in the near-field plume. It is found that the ion acoustic modes give rise to an enhanced effective collision frequency in the direction parallel to the applied magnetic field that exceeds the classical collision frequency by two orders of magnitude. The anti-drift waves promote an anisotropic collision frequency that depends on the direction of the electron drift. While the enhanced collision frequency from these waves is comparable to the classical frequency for motion along the applied magnetic field, the effective collision frequency in the azimuthal direction exceeds the classical by three orders of magnitude. These results are discussed in the context of their impact on the steady-state plasma gradients in the near-field cathode plume. Closure models for incorporating the effective collision frequencies from both types of waves into fluid-based codes are derived and shown to agree with the measured wave-driven collision frequencies.

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Counterstreaming ions at the inner pole of a magnetically shielded Hall thruster

Huang

Kamhawi

2021

Journal of Applied Physics

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During development testing of a 12.5 kW magnetically shielded Hall thruster, direct evidence of counterstreaming ions eroding the pole covers was found. One stream of ions appears to originate from the discharge channel while the other stream appears to originate from the centrally mounted cathode. Velocity distribution measurement indicates that each stream impacts the poles of the thruster at high oblique angles of incidence. While the average energy of each stream was in the tens of eV, the energy distributions contained high-energy tails that can be a major contributor to erosion. Starting with the physical picture of high oblique angle bombardment, predictions of change in erosion behavior over time are in good agreement with pole cover erosion measurements taken during wear testing. The new evidence points to a need to study these ions that are traditionally considered “low-energy” ions and the role they play in the erosion of the poles of magnetically shielded Hall thrusters.

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Evidence of Counter-Streaming Ions near the Inner Pole of the HERMeS Hall Thruster

Cited by 7 publications

References 18 publications

Use of an accelerated testing method to characterize inner front pole cover erosion in a high power Hall thruster

Use of an accelerated testing method to characterize inner front pole cover erosion in a high power Hall thruster

Non-classical electron transport in the cathode plume of a Hall effect thruster

Counterstreaming ions at the inner pole of a magnetically shielded Hall thruster

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