Low-frequency azimuthal stability analysis of Hall thrusters

Escobar, Diego A.; Ahedo, Eduardo

doi:10.2514/6.2012-4180

Cited by 4 publications

(5 citation statements)

References 30 publications

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“…Moreover, curvature effects in the azimuthal direction are also neglected as the mean radius of the channel is typically larger than the width of the channel. Obviously, in the limit of a stationary and axi-symmetric solution the system of equations (1) reduces to the 1D model.…”

Section: A General 2d Formulationmentioning

confidence: 99%

“…Equations (1) can be rewritten in a form more amenable to the current study. To this end, the partial derivatives with respect to the time and the azimuthal coordinate are moved to the right hand side of the equations.…”

Section: A General 2d Formulationmentioning

confidence: 99%

“…electric and magnetic field f 0 zero-th order solution of macroscopic variable f f perturbation of macroscopic variable f f 1 coefficient of Fourier-like perturbation of macroscopic variable f n, n n plasma and neutral density v j velocity vector of species j v jx , v jy axial and azimuthal velocity of species j T e , ϕ electron temperature and electric potential ν i , ν e ionization frequency and overall electron-neutral collision frequency ν w , ν we particle and energy wall-loss frequencies E ′ i energy loss per actual ionization ω, k angular frequency and azimuthal wave number of perturbation χ…”

Section: Nomenclaturementioning

confidence: 99%

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Analysing the Azimuthal Spoke Oscillation of Hall Thrusters via Numerical Simulation

Anton¹,

Ahedo

2014

50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

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This paper presents results obtained from numerical simulations of the spoke oscillation with a linearised time-dependent 2D code of the Hall discharge. These results are used to analyze the mechanism of the spoke from a physical point of view. There exist several hints pointing to a connection with an azimuthal variation of the ionization process and this is investigated in detail here. Moreover, the influence on the spoke properties of different operating parameters such as discharge voltage, mass flow, magnetic field, and thruster size is analysed by means of various parametric variations. The work presented here builds on previous studies by the authors 1, 2 where the azimuthal stability of the Hall discharge was analysed from a global point of view, as opposed to the more common local stability analyses. The simulations in Ref.[2] show both axial and azimuthal oscillations in the low frequency regime, typically known as breathing mode and spoke respectively. One of the drawbacks of the formulation used in Ref.[2] is the lack of heat conduction terms in the model causing large temperature gradients and a narrow ionization region. These issues are resolved in the current study by modifying the formulation and solution method in order to include heat conduction terms. Additionally, a comparison of the results obtained from local and global stability analyses is also presented here.

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Section: A General 2d Formulationmentioning

confidence: 99%

Section: A General 2d Formulationmentioning

confidence: 99%

Section: Nomenclaturementioning

confidence: 99%

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Analysing the Azimuthal Spoke Oscillation of Hall Thrusters via Numerical Simulation

Anton¹,

Ahedo

2014

50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

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“…This shift is accompanied by slight changes in the characteristic lengths of these plasma parameter profiles. As both wall interactions and plasma gradients have been identified as potential drivers for low-frequency oscillations in Hall thrusters, 11,21,[31][32][33][34][35] it is reasonable to expect these changes may result in significant differences in the oscillation spectrum of MS thrusters. The study of the H6MS is an expedient choice for identifying these differences as the unshielded variation of the thruster, the H6US, has been the subject of an extensive study of low-frequency oscillations.…”

Section: B H6 Hall Thrustermentioning

confidence: 99%

Low Frequency Plasma Oscillations in a 6-kW Magnetically Shielded Hall Thruster

Jorns

Hofer

2013

49th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

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The oscillations from 0-100 kHz in a 6-kW magnetically shielded thruster are experimentally characterized. Changes in plasma parameters that result from the magnetic shielding of Hall thrusters have the potential to significantly alter thruster transients. A detailed investigation of the resulting oscillations is necessary for the purpose of determining the underlying physical processes governing time-dependent behavior in magnetically shielded thrusters as well as for improving thruster models. In this investigation, a high speed camera and a translating ion saturation probe are employed to examine the spatial extent and nature of oscillations from 0-100 kHz in the H6MS thruster. Two modes are identified at 7-12 kHz and 75-90 kHz. The low frequency mode is azimuthally uniform across the thruster face while the high frequency oscillation is concentrated close to the centerline-mounted cathode with an m = 1 azimuthal dependence. These experimental results are discussed in the context of wave theory as well as published observations from an unshielded variant of the H6MS thruster. Nomenclature B 0 Background magnetic field c s Ion sound speed E r Electric field in radial direction f b Breathing mode frequency F Fourier transform with respect to time I v (r, θ, t) Light intensity at position (r, θ) and time t I v (r, θ) Mean light intensity at position (r, θ) I v (r, θ, t) Light intensity normalized by the mean value I r,j Azimuthally binned light intensity i sat (r, t) Ion saturation current at radius r and fixed axial position i sat (r, t) Mean ion saturation current at radius r and fixed axial position I sat (r, t) Ion saturation current normalized by the mean value k z Component of wavenumber in axial direction L i Length of ionization zone m e,i Electron, ion mass N b Number of azimuthal bins n e,i Electron, ion density q Fundamental charge * Associate Engineer,

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“…Because the simulation model ignores azimuthal fluctuations, the Bohm diffusion was employed to compensate for the reduced electron mobility across the magnetic field. Although the anomalous electron transport remains to be an open question that there are various discussions about which and how to explain and employ the model, [24][25][26] it is beyond the scope of this work to further investigate on the Bohm diffusion model itself. Thus, the conventional Bohm diffusion model with the constant coefficient of 1/16 was employed.…”

Section: A Overview Of Simulation Modelmentioning

confidence: 99%

Kinetic particle simulation of discharge and wall erosion of a Hall thruster

Cho

Komurasaki²,

Arakawa

2013

Physics of Plasmas

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The primary lifetime limiting factor of Hall thrusters is the wall erosion caused by the ion induced sputtering, which is predominated by dielectric wall sheath and pre-sheath. However, so far only fluid or hybrid simulation models were applied to wall erosion and lifetime studies in which this non-quasi-neutral and non-equilibrium area cannot be treated directly. Thus, in this study, a 2D fully kinetic particle-in-cell model was presented for Hall thruster discharge and lifetime simulation. Because the fully kinetic lifetime simulation was yet to be achieved so far due to the high computational cost, the semi-implicit field solver and the technique of mass ratio manipulation was employed to accelerate the computation. However, other artificial manipulations like permittivity or geometry scaling were not used in order to avoid unrecoverable change of physics. Additionally, a new physics recovering model for the mass ratio was presented for better preservation of electron mobility at the weakly magnetically confined plasma region. The validity of the presented model was examined by various parametric studies, and the thrust performance and wall erosion rate of a laboratory model magnetic layer type Hall thruster was modeled for different operation conditions. The simulation results successfully reproduced the measurement results with typically less than 10% discrepancy without tuning any numerical parameters. It is also shown that the computational cost was reduced to the level that the Hall thruster fully kinetic lifetime simulation is feasible. V C 2013 AIP Publishing LLC. [http://dx

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Low-frequency azimuthal stability analysis of Hall thrusters

Cited by 4 publications

References 30 publications

Analysing the Azimuthal Spoke Oscillation of Hall Thrusters via Numerical Simulation

Analysing the Azimuthal Spoke Oscillation of Hall Thrusters via Numerical Simulation

Low Frequency Plasma Oscillations in a 6-kW Magnetically Shielded Hall Thruster

Kinetic particle simulation of discharge and wall erosion of a Hall thruster

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