Measurements of Secondary Electron Emission Effects in the Hall Thruster Discharge

Raitses, Y; Smirnov, A; Staack, D; Fisch, N J

doi:10.2172/934610

Cited by 5 publications

(7 citation statements)

References 14 publications

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“…3, the peak electron temperature for each throttling condition is plotted scaled with the discharge voltage. We compare this with the trend noted in [38][39], where it is stated that the peak electron temperature stays roughly proportional (by a factor of approximately 0.12) to the discharge voltage for a wide variety of examined thrusters. It can be observed that the over-estimation of the peak electron temperature with respect to the experimental results occurs in all cases, except for the 400V-3kW case.…”

Section: Fig 2 Left: Plasma Potential and Electron Temperature In Tsupporting

confidence: 57%

Numerical simulations of the XR-5 Hall thruster for life assessment at different operating conditions

Ortega

Jorns

Mikellides

et al. 2015

51st AIAA/SAE/ASEE Joint Propulsion Conference

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NASA's Jet Propulsion Laboratory has been investigating the applicability of Aerojet Rocketdyne's XR-5 thruster, a 4.5 kW class Hall thruster, for deep-space missions. Major considerations for qualifying the XR-5 for deep-space missions are demonstration of a wide throttling envelope and a usable life capability in excess of 10,000 h. Numerical simulations with the 2-D axisymmetric code Hall2De are employed to inform the qualification process by assessing erosion rates at the thruster surfaces in a wide range of throttling conditions without the need for conducting costly endurance testing. In previous work at JPL by Jorns et al., the anomalous collision frequency distribution for 11 different throttling conditions of the XR-5 spanning 0.3-4.5 kW were identified based on probe measurements of the electron temperature in the near plume region. In this paper, we provide estimates for the erosion rates at the channel walls and pole covers for the same 11 conditions. Uncertainties in the plasma measurements and in the anomalous collision frequency distribution are addressed by determining upper and lower bounds of the erosion rates. Results suggest that erosion of the walls only occurs in the last 5% of the acceleration channel and the rate of such erosion decreases as the geometry of the thruster changes in time due to magnetic shielding. A quasi-zero-erosion state is eventually achieved in all the examined throttling conditions. Examination of the results for pole surface erosion and estimated cathode life indicates that the XR-5 propellant throughput capability will exceed 700 kg, which provides 50% margin over the usable throughput capability of 466 kg as already demonstrated in wear testing

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Section: Fig 2 Left: Plasma Potential and Electron Temperature In Tsupporting

confidence: 57%

Numerical simulations of the XR-5 Hall thruster for life assessment at different operating conditions

Ortega

Jorns

Mikellides

et al. 2015

51st AIAA/SAE/ASEE Joint Propulsion Conference

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“…Modeling indicated that the presence of low secondary electron emission (SEE) material in the channel could have been responsible for shifting the acceleration region upstream and reducing the plume divergence [7]. Recent experimental results have demonstrated the effect of low SEE carbon electrodes on the electron temperature [8], in qualitative agreement with several thruster models [9][10][11]. Modeling by Fruchtman et al suggests that an electrode in the channel may enhance efficiency and provide control of the electric field profile in the thruster [12].…”

mentioning

confidence: 72%

Segmented Electrode Hall Thruster

Diamant¹,

Pollard²,

Cohen³

et al. 2006

Journal of Propulsion and Power

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Thrust, thrust efficiency, and plume divergence were measured for a 9 cm diam laboratory model Hall thruster with segmented electrodes in the discharge channel. Several geometries with graphite nonemissive electrodes, and one with a tungsten emissive electrode were tested and compared to a baseline configuration with all electrodes replaced by boron nitride segments. To within measurement uncertainty, thrust and thrust efficiency were unaffected by insertion of electrodes, with the exception of reduced efficiency for a configuration which resulted in a 20% increase in discharge current. Maximum plume half-angle reductions of 4 deg were obtained with emissive and nonemissive electrodes.

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“…It has been concluded that only the plasma azimuthal fluctuations are responsible for anomalous electron transport inside and outside the Hall thruster channel. Nevertheless, changing the wall material of Hall thrusters results in significant plasma parameters and electron axial current changes [30][31][32]. Then, there are strong arguments to conclude that the azimuthal fluctuations could be induced by surface effects.…”

Section: The Anomalous Electron Cross-field Conductivitymentioning

confidence: 99%

Particle‐in‐Cell Simulation of Stationary Plasma Thruster

Taccogna¹,

Longo

Capitelli

et al. 2007

Contrib. Plasma Phys.

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A very good example for the application of PIC techniques for detailed studies of low-temperature plasmas is the Hall thrusters. Here, a variety of models with different complexities are needed to get better insight into the physics of these systems. Particular emphasis has been spent for the geometrical scaling, for the simulation of the plasma-wall interaction inside the acceleration channel and for ion-neutral collision into the plume emitted from the thruster. Results show the axial acceleration mechanism, the secondary electron emission instability, the azimuthal fluctuations into the channel and the ion backflow and electron trapping in the plume. However, until now, many propulsive systems have employed a solid, liquid or gaseous propellant and chemical propulsion to equip launcher spacecrafts for interplanetary missions and satellites. Alternatively, many electric systems have been proposed for satellite propulsion (microwave, arc-jet, stationary plasma thruster (SPT), pulsed plasma thruster (PPT), thruster with electric field (FEEP), gridded ion thruster, etc.) or for planetary missions (magneto-plasma-dynamic thruster (MPD)). Among these plasma sources, the Stationary Plasma Thruster (SPT) is one of the more promising devices for satellite station keeping, in particular due to the gain in mass (around 300 kg for a 3t-class satellite) and a long lifetime (up to 7000 h). Since 1970, almost 90 SPT thrusters have been tested on board Russian satellites (Meteor, Galls) and nowadays, all space agencies recognize the usefulness of SPTs for North-South, East-West (NS-EW) station keeping or attitude control of geostationary telecommunication satellites. The SPT was successfully used in the European lunar probe mission SMART1 and has been proposed for the future satellite constellations. In order to study and to manufacture Hall thrusters, a large effort is now being made in Europe, Russia, Japan and USA, while some other countries such as China, India and Israel are also interested in applying electric propulsion to spacecraft.A SPT [1], also known as Hall effect thruster (HET) or thruster with closed electron drift, can be schematically described (figure 1) as an anode-cathode system, with a dielectric annular chamber where the propellant ionization and acceleration process occurs. This thruster works using a perpendicular electric and magnetic fields configuration. A magnetic circuit generates an axis-symmetric and quasi-radial magnetic field between the inner and outer poles. In operation, an electrical discharge is established between an anode (deep inside the channel), which is acting also as a gas distributor, and an external cathode, which is used also as an electron emitter. In this configuration, cathode electrons are drawn to the positively charged anode, but the radial magnetic field creates large impedance, trapping the electrons in cyclotron motion which follows a closed drift path inside the annular chamber. The trapped electrons act as a volumetric zone of ionization for neutral propellant atoms a...

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Measurements of Secondary Electron Emission Effects in the Hall Thruster Discharge

Cited by 5 publications

References 14 publications

Numerical simulations of the XR-5 Hall thruster for life assessment at different operating conditions

Numerical simulations of the XR-5 Hall thruster for life assessment at different operating conditions

Segmented Electrode Hall Thruster

Particle‐in‐Cell Simulation of Stationary Plasma Thruster

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