Myxine design for an experimental Galathea reactor

Морозов, А. И.; Nevrovskii, V. A.; Pistunovich, V.I.; Svechkopal, A. N.

doi:10.1134/1.1259329

Cited by 19 publications

(30 citation statements)

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“…3,11 It must be underlined, however, that such a study cannot pretend to provide more than qualitative insights. Even though the general transit-time mechanism outlined is expected to be valid for all modes, quantitative predictions for the fundamental transit-time mode are, in nature, very unreliable, owing to its low frequency and long wavelength.…”

Section: Discussionmentioning

confidence: 94%

“…Since the phase velocity of ion acoustic waves, V ± C, is of the order of the ion velocity in the acceleration region of Hall thrusters, the proposed mechanism seems adequate to qualitatively explain experimentally measured frequencies. 3 The onset of this instability was shown to involve the amplification of acoustic waves, the spatial growths of which are governed by the ion current fraction and by the intensity of the local ionization, synthesized in a single parameter,…”

Section: Discussionmentioning

confidence: 99%

“…1,2 The so-called transit-time instability has been experimentally identified as a longitudinal mode involving ion dynamics, with a frequency in the 100-500-kHz band. [3][4][5][6][7] Interestingly, an ion-transit instability has also been repeatedly reported in numerical simulations. [8][9][10][11] Although a candidate explanation of the transit-time mechanism was first proposed by Esipchuk in his generalization of Morozov's earlier stability study, 12,13 some issues with its mathematical treatment have been pointed out ͑cf.…”

Section: Introductionmentioning

confidence: 93%

“…In the following, the original variable names have been preserved. 12 Starting from Morozov's initial equation system,…”

Section: Appendix: Consistency Of Local Stability Criteria In Nonunifmentioning

confidence: 99%

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Transit-time instability in Hall thrusters

Barral

Makowski²,

Peradzyński

et al. 2005

Physics of Plasmas

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Longitudinal waves characterized by a phase velocity of the order of the velocity of ions have been recurrently observed in Hall thruster experiments and simulations. The origin of this so-called ion transit-time instability is investigated with a simple one-dimensional fluid model of a Hall thruster discharge in which cold ions are accelerated between two electrodes within a quasineutral plasma. A short-wave asymptotics applied to linearized equations shows that plasma perturbations in such a device consist of quasineutral ion acoustic waves superimposed on a background standing wave generated by discharge current oscillations. Under adequate circumstances and, in particular, at high ionization levels, acoustic waves are amplified as they propagate, inducing strong perturbation of the ion density and velocity. Responding to the subsequent perturbation of the column resistivity, the discharge current generates a standing wave, the reflection of which sustains the generation of acoustic waves at the inlet boundary. A calculation of the frequency and growth rate of this resonance mechanism for a supersonic ion flow is proposed, which illustrates the influence of the ionization degree on their onset and the approximate scaling of the frequency with the ion transit time. Consistent with experimental reports, the traveling wave can be observed on plasma density and velocity perturbations, while the plasma potential ostensibly oscillates in phase along the discharge.

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Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 93%

“…In the following, the original variable names have been preserved. 12 Starting from Morozov's initial equation system,…”

Section: Appendix: Consistency Of Local Stability Criteria In Nonunifmentioning

confidence: 99%

See 2 more Smart Citations

Transit-time instability in Hall thrusters

Barral

Makowski²,

Peradzyński

et al. 2005

Physics of Plasmas

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“…Xhese are so-called transit time oscillations which were observed in experiments [7,8], predicted by numerical models [9], and analyzed theoretically [10]. In our previous experiment with PPS®-100 HEX [5] the oscillations of this ME range could be resolved due to the use of empirical mode decomposition (EMD) method [11] however, just for PPS®-XOOO HEX operating at high voltage oscillations of ME range can be strong enough to be resolved with visual inspection of signals and even mask the slow breathing mode.…”

Section: Introductionmentioning

confidence: 95%

Where is the breathing mode ? High voltage Hall effect thruster studies with EMD method

Kurzyna¹,

Makowski²,

Peradzyński

et al. 2008

AIP Conference Proceedings

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Discharge current and local plasma oscillations are studied in a high voltage Hall effect thruster PPS®-XOOO. Characteristic time scales that appear in different operating conditions are resolved with the use of Hilbert-Huang spectra (HHS) which display time dependenc of instantaneous frequency and power. Sets of intrinsic mode functions (i'm/s) that are used for HHS calculation result due to application of empirical mode decomposition method (EMD) to nonstationary multicomponent signals. In the experiment the signals are captured in the electric circuit of the thruster as well locally, in the vicinity of the thruster exhaust region. Classical electric probes spaced along the azimuth and/or thruster axis let us study correlations of signals which were captured in different locations. In this way azimuthal and axial propagation of disturbances is inspected. The discharge voltage is varied in the range of 200 -^ 900 V while xenon mas flow rate of 5 -^ 9 mg/s. LF, MF, and HF characteristic bands that are known from previous studies of PPS®-100 thruster have been also detected here. However, expanding discharge current onto a set of intrinsic modes we can resolve MF mode more reliably than before. Moreover, for higher discharge voltages, this irregular mode turns into more regular waveform and tends to dominate in the discharge current masking almost completely the breathing mode (LF oscillations of the discharge current). In such a case triggering of HF oscillations is correlated with the phase of MF mode while in the case of PPS®-100 thruster it was correlated with the appropriate phase of the breathing mode (LF band). Regular HF emission that can be unambiguously interpreted as azimuthal electrostatic wave now is observed only in the specific operating conditions of the thruster. However, even if irregular HF emission is observed the time delay of cross-correlated signals which are captured in different azimuthal locations corresponds to the velocity of azimuthal electron drift in the field of magnetic barrier.

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Growth of resistive instabilities in E×B plasma discharge simulations

et al. 2008

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Two-dimensional hybrid numerical simulations of E ϫ B discharges used in Hall thruster propulsion point to the presence of strong fluctuations attributable to resistive instabilities in the frequency range of f Ϸ 0.1-10 MHz and the wavenumber range of −1 Ϸ 10-500 m −1. Analytical analyses confirm that these resistive modes are of the convective type, become increasingly unstable at low electron mobility, and are particularly intense at high voltage. The simulations, which model cross-field electron flow via an experimentally measured mobility, exhibit large fluctuation power in a region corresponding to a strong electron transport barrier. The analysis gives an electron mobility ͑ e ͒-dependent growth rate ͑␥͒ scaling as ␥ ϳ e −1/2. The predicted phase velocity of these waves is close to the ion velocity, somewhat lower than that seen in the simulations. Including the electron pressure contribution lowers the growth rate at high frequencies, and introduces a phase velocity that is shifted by ± the ion acoustic speed for the stable and unstable branch, respectively. Surprisingly, the phase velocity of the strong disturbances at high frequency seen in the simulations is found to be in agreement with that of the initially stable branch. Finite ionization/particle wall recombination does not change the overall conclusions at high frequencies. However, at lower f or larger , the growth rate of the instability is dominated by the ionization rate, and the disturbances are better described as "ionization" instabilities. The transition/competition between ionization, electron pressure, and resistive behavior gives rise to a "quiescent frequency band" where the growth rate is found to be small, consistent with what is seen in the numerical experiments. While simple linear analysis captures much of the observed simulation behavior, comparison with limited experimental data at low frequency suggests that other effects, in particular azimuthal dynamics, are very important, and further motivate extending the hybrid simulation models to three dimensions.

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Myxine design for an experimental Galathea reactor

Cited by 19 publications

References 0 publications

Transit-time instability in Hall thrusters

Transit-time instability in Hall thrusters

Where is the breathing mode ? High voltage Hall effect thruster studies with EMD method

Growth of resistive instabilities in E×B plasma discharge simulations

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