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

Jorns, Benjamin; Cusson, Sarah E.; Brown, Zachariah; Dale, Ethan T.

doi:10.1063/1.5130680

Cited by 37 publications

(17 citation statements)

References 49 publications

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“…Ref. [152]), which can be leveraged to relate transport coefficients such as an anomalous collision frequency to wave amplitude and growth rate. Ideally, this method requires simultaneous measurements of the electric field and density fluctuations associated with the waves.…”

Section: State Of the Art And Recent Progressmentioning

confidence: 99%

“…13 (b), illustrates how these MHz fluctuations exhibit an additional kHz range modulation (measurable due to the fluctuations in density as spokes traverse the measurement region). Recent experimental work on hollow cathodes operating in conjunction with a Hall thruster also showed that not only does plasma turbulence dominate the electron transport in the cathode, but it also may be linked to lower-frequency oscillations [151], [152]. Taken together, these experimental results from cathodes, Hall thrusters, and magnetrons now point to the conclusion that turbulence-driven transport has a critical role in governing both the steadystate plasma properties as well as the transient, large scale oscillations discussed in Sec.…”

Section: State Of the Art And Recent Progressmentioning

confidence: 99%

“…In these previous works, experimental measurements of the evolution of a turbulence and anomalous transport in both space and time were leveraged to guide the development of fluid codes that included equations to approximate the effects of plasma turbulence on electron resistivity [84], [151], [152], [155], [168], [169]. These models in turn have been successfully used to simulate the plasma in both the interior and exterior of the cathode.…”

Section: Current and Future Challengesmentioning

confidence: 99%

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

et al. 2020

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This paper provides perspectives on recent progress in the understanding of the physics of devices where the external magnetic field is applied perpendicularly to the discharge current. This configuration generates a strong electric field, which acts to accelerates ions. The many applications of this set up include generation of thrust for spacecraft propulsion and the separation of species in plasma mass separation devices. These "E×B" plasmas are subject to plasma-wall interaction effects as well as various micro and macro instabilities, and in many devices, we observe the emergence of anomalous transport. This perspective presents the current understanding of the physics of these phenomena, state-of-the-art computational results, identifies critical questions, and suggests directions for future research.

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Section: State Of the Art And Recent Progressmentioning

confidence: 99%

Section: State Of the Art And Recent Progressmentioning

confidence: 99%

Section: Current and Future Challengesmentioning

confidence: 99%

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

et al. 2020

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“…The contribution of the IAT to the total electron collision frequency can be estimated by the anomalous collision frequency, ν IAT an . Assuming that in an experimental context ñe / n e ≈ Ĩsat /I sat,0 [32], where I sat is the ion saturation current collected by the probe with its mean value I sat,0 , the anomalous collision frequency has the following expression [30]:…”

Section: Governing Equations For Cathode Plume Electron Transport And...mentioning

confidence: 99%

Ionization instability and turbulence in the plume of sub-ampere hollow cathodes with applied magnetic field

Potrivitu

2022

Preprint

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When operated with a Hall thruster, either centrally or externally mounted, cathode discharge occurs in a magnetic field environment. Therefore, it is important to assess the influence of the magnetic field on the standalone operation of a hollow cathode to better predict device behavior when coupled with a Hall thruster. This study focuses on the influence of an applied axial magnetic field on main oscillatory phenomena in the plume of a Kr-fed sub-ampere hollow cathode. A probe array consisting of two cylindrical Langmuir probes and an emissive probe was used to assess changes in the plasma parameters and collected ion saturation current as the magnetic field strength was increased. The electron transport along the cathode-anode space was analyzed in terms of total electron collision frequency. It was shown that a higher magnetic field strength induces larger plasma densities and lower electron temperatures. Both the ionization instability and ion acoustic turbulence (IAT) energy diminished with higher magnetic field strengths when the cathode operated in plume mode before the magnetic field was applied. The total electron collision frequency as well as its main contributor, the anomalous collision frequency due to IAT, decreased at higher field strengths. Higher magnetic field strengths were shown to damp the ionization instability. The results included in this communication are the first characterization of the response

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“…Anomalous electron transport has been strongly linked to plasma oscillations in HTs [5] in both the thruster discharge channel [6,7] and cathode regions [8]. Long-wavelength azimuthal oscillations, the focus of this work, are typically characterized in a Fourier representation with integer mode numbers, m, including the azimuthally uniform m = 0 "breathing" modes in HT channels [9,10] and cathodes [11,12], m > 0 azimuthally rotating "spoke" modes in the channel, and a m = 1 counter rotating "antidrift" modes around the cathode [13].…”

Section: Introductionmentioning

confidence: 99%

A comparison of Fourier and POD mode decomposition methods for high-speed Hall thruster video

Brooks¹,

McDonald²,

Kaptanoglu³

2022

Preprint

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Hall thrusters are susceptible to large-amplitude plasma oscillations that impact thruster performance and lifetime and are also difficult to model. High-speed cameras are a popular tool to study these dynamics due to their spatial resolution and are a popular, nonintrusive complement to in-situ probes. Highspeed video of thruster oscillations can be isolated (decomposed) into coherent structures (modes) with algorithms that help us better understand the evolution and interactions of each. This work provides an introduction, comparison, and step-by-step tutorial on established Fourier and newer Proper Orthogonal Decomposition (POD) algorithms as applied to high-speed video of the unshielded H6 6-kW laboratory model Hall thruster. From this dataset, both sets of algorithms identify and characterize m = 0 and m > 0 modes in the discharge channel and cathode regions of the thruster plume, as well as mode hopping between the m = 3 and m = 4 rotating spokes in the channel. The Fourier methods are ideal for characterizing linear modal structures and also provide intuitive dispersion relationships. By contrast, the POD method tailors a basis set using energy minimization techniques that better captures the nonlinear nature of these structures and with a simpler implementation. Together, the Fourier and POD methods provide a more complete toolkit for studying Hall thruster plasma instabilities and mode dynamics. Specifically, we recommend first applying POD first to quickly identify the nature and location of global dynamics and then using Fourier methods to isolate dispersion plots and other wave-based physics.

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

Cited by 37 publications

References 49 publications

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

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

Ionization instability and turbulence in the plume of sub-ampere hollow cathodes with applied magnetic field

A comparison of Fourier and POD mode decomposition methods for high-speed Hall thruster video

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