Low frequency azimuthal stability of the ionization region of the Hall thruster discharge. I. Local analysis

Escobar, Diego A.; Ahedo, Eduardo

doi:10.1063/1.4870963

Cited by 25 publications

(48 citation statements)

References 40 publications

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“…3 and 4, the azimuthal oscillation is due to an azimuthal variation of the ionization process. The connection between the spoke oscillation and the ionization process had already been suggested theoretically in [35] and [48], and, based on experiments, by other researchers [49]. This fact is further analyzed in Section III-C, Table I and the same conditions as in Fig.…”

Section: B Azimuthal Oscillationsmentioning

confidence: 56%

“…Beyond this, we identify the following areas of research. First, a comparison between the stability criteria derived from the local stability analyses of [29]- [31] and [35] and the results from the global stability presented here seems very appealing. This can be achieved by analyzing the local stability of the axial profiles of the reference case and comparing the results against the global ones presented here.…”

Section: Discussionmentioning

confidence: 98%

“…The latter are based on the analysis of the fluid equations at a fixed axial location of the channel and this requires freezing the macroscopic plasma variables and their derivatives, whereas the former method does account consistently for the axial variation of those variables and their linear perturbations. Most of the stability analyses of the Hall discharge in the azimuthal direction carried out so far are local and can be grouped in those that do not account for the ionization process [8], [27]- [31] and those that take it into consideration in the model through particle source terms and fluid equations for the neutral species [17], [32]- [35]. However, all these local stability studies suffer from the problems mentioned above.…”

Section: Introductionmentioning

confidence: 99%

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Global Stability Analysis of Azimuthal Oscillations in Hall Thrusters

Escobar

Ahedo

2015

IEEE Trans. Plasma Sci.

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A linearized time-dependent 2-D (axial and azimuthal) fluid model of the Hall thruster discharge is presented. This model is used to carry out a global stability analysis of the plasma response, as opposed to the more common local stability analyses. Experimental results indicate the existence of low-frequency long-wave-length azimuthal oscillations in the direction of the E × B drift, usually referred to as spokes. The present model predicts the presence of such oscillations for typical Hall thruster conditions with a frequency and a growth rate similar to those found in experiments. Moreover, the comparison between the simulated spoke and the simulated breathing mode, a purely axial low-frequency oscillation typical in Hall thrusters, shows similar features in them. Additionally, the contribution of this azimuthal oscillation to electron conductivity is evaluated tentatively by computing the equivalent anomalous diffusion coefficient from the linear oscillations. The results show a possible contribution to anomalous diffusion in the rear part of the thruster.

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Section: B Azimuthal Oscillationsmentioning

confidence: 56%

Section: Discussionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Global Stability Analysis of Azimuthal Oscillations in Hall Thrusters

Escobar

Ahedo

2015

IEEE Trans. Plasma Sci.

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“…Note that in order to consider consistently the axial gradients of the variables in this linearization, the zero-th order solution and the coefficients of the Fourier expansion of the perturbations must retain the dependence on the axial coordinate. This is the main difference with respect to local stability analyses such as the one previously carried out by the authors 31 .…”

Section: B Linearised Governing Equationsmentioning

confidence: 95%

“…The latter are based on the analysis of the fluid equations at a fixed axial location of the channel and need to freeze the macroscopic plasma variables and their derivatives, whereas the former method does account consistently for the axial variation of those variables and their linear perturbations. Most of the stability analyses of the Hall discharge in the azimuthal direction carried out so far are local and can be grouped in those that do not account for the ionization process [21][22][23][24][25][26][27] and those that take it into consideration in the model through particle source terms and fluid equations for the neutral species 6,[28][29][30][31] . However, all these local stability studies suffer from the problems mentioned above.…”

Section: Introductionmentioning

confidence: 99%

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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Study of low‐frequency oscillations in a double‐stage Hall thruster

Zhang

Ding

Han

et al. 2017

Contributions to Plasma Physics

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The characteristics of low-frequency oscillations of double-stage Hall thrusters are quite different from those of conventional single-stage Hall thrusters. In this paper, the effects of double-stage discharge on the low-frequency oscillations are experimentally investigated. The results indicate that the amplitude significantly decreases with increasing magnetic field strength and voltage during the ionization stage. Meanwhile, data analysis reveals that ionization occurs in both stages and that the transport ion current between the two stages is the key factor that affects the amplitude and main frequency of the oscillations. Two new processes, namely the ion transport and ion recombination caused by double-stage discharge, are found to be relevant to the change in the current oscillations. To summarize, the ionization stage relieves the oscillations in the acceleration stage, leading to a reduction in the amplitude of the discharge current. KEYWORDS Double-stage Hall thruster, Ion transport current, Low-frequency oscillation INTRODUCTIONIt has been proved that Hall effect thrusters (HETs) are suitable for space missions, such as orbit transfer and station keeping, owing to their high thrust density and medium specific impulse. However, future space missions require multimode Hall thrusters with flexible working conditions. [1,2] In order to control the ionization and acceleration processes independently, double-stage Hall thrusters (DSHTs) have been proposed as a new generation of thrusters for multiple working modes. [3][4][5] The ionization and acceleration processes in DSHTs are divided into two stages. Several characteristics change because of the separation of the ionization and acceleration process, especially low-frequency oscillations. [3,5] It is observed that the amplitude of the low-frequency current oscillations in a DSHT is usually small and affected by the double-stage discharge condition.[3,6] Bugrova et al. studied a DSHT, called SPT-MAG, and reported very small low-frequency current oscillations with a relative standard deviation of 1-4%.[4] They attributed the improved stability to the specially organized ionization stage, where more than 90% of the propellant was ionized. [3,4] Hirohisa et al. investigated a microwave discharge DSHT and reported that microwave injection obviously suppressed current oscillations. Propellants are ionized near the anode because of the microwave-excited surface-wave plasmas, and the ions are accelerated in the E × B field. The high-speed ion flow is considered to reduce the time lag between the gas and ion feeds, leading to a reduced current oscillation.[6] The low-frequency oscillations significantly affect the performance of HETs and have been widely studied both theoretically [7][8][9][10] and experimentally. [11,12] However, although the amplitude of the current oscillations is found to be suppressed by a double-stage discharge in the literature, there is no scientific study on the mechanism of the current suppression. With the development of DSHT technology...

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Low frequency azimuthal stability of the ionization region of the Hall thruster discharge. I. Local analysis

Cited by 25 publications

References 40 publications

Global Stability Analysis of Azimuthal Oscillations in Hall Thrusters

Global Stability Analysis of Azimuthal Oscillations in Hall Thrusters

Analysing the Azimuthal Spoke Oscillation of Hall Thrusters via Numerical Simulation

Study of low‐frequency oscillations in a double‐stage Hall thruster

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