Correlation of Direct and Remote Measurements on a Hollow Cathode Plasma Discharge

Farnell, Casey C.; Williams, John D.

doi:10.1109/ppps.2007.4345778

Cited by 4 publications

(9 citation statements)

References 1 publication

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“…Researchers have measured the electron temperature upstream and downstream of the cathode tip [25,26]. Frequently, the electron temperature is of the order 1 eV inside the cathode, increasing to >5 eV downstream [25]. In the present simulation, the detailed physics of the cathode discharge are not modelled.…”

Section: Resultsmentioning

confidence: 99%

“…For all of the results of computations shown below, the cathode was placed in the domain at x = 80 mm, y = 0 mm and z = 20 mm as this is the actual experimental placement for the Hall thruster simulated. Researchers have measured the electron temperature upstream and downstream of the cathode tip [25,26]. Frequently, the electron temperature is of the order 1 eV inside the cathode, increasing to >5 eV downstream [25].…”

Section: Resultsmentioning

confidence: 99%

“…We take θ = 135 • and the standard deviation of the angular spread of the electrons to be 30 • . This distribution was based on density measurements [25] which indicate a distribution which is neither a narrow beam nor a very diffuse cloud. Electrons emitted from the cathode are given an additional energy 'kick' along their initial direction with a magnitude equal to the plasma potential at the point of emission (in the present simulation, the kick is of order 10 eV).…”

Section: Resultsmentioning

confidence: 99%

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Single particle simulations of electron transport in the near-field of Hall thrusters

Smith¹,

Cappelli²

2010

J. Phys. D: Appl. Phys.

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The results of 3D, single particle electron trajectory calculations are presented for the near-field of a laboratory E × B Hall plasma thruster. For a prescribed static magnetic and electric field distribution, single electrons are launched and tracked from a simulated cathode. Collisions with external thruster surfaces are accounted for; however, field fluctuations are disregarded. Bulk statistics including the channel to beam electron current ratio, electron lifetimes and spatial distributions of the number density, mean energy, energy distributions, velocity distributions and velocity component ratios are catalogued. For conditions typical of a moderate power Hall thruster, the mean lifetime of electrons in the domain of axial scale length, L = 0.3 m, is approximately 120 ns. Electrons which eventually enter the channel are found to strike the thruster ∼10 3 times as frequently as electrons which exit the domain in the plume. For the static E and B field distributions used in this study, the channel to beam current ratio is found to be on the order of 0.1 and the velocity ratio, V E /V E×B , over the channel has a mean of ∼0.5, with higher values driven largely by collisions with the thruster indicating the importance of such events in driving transport into the channel.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Single particle simulations of electron transport in the near-field of Hall thrusters

Smith¹,

Cappelli²

2010

J. Phys. D: Appl. Phys.

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“…For the measurements presented herein, plasma potential was measured using a high speed data acquisition system connected to the probe thorough a high-impedance, lowcapacitance, active filter ( [15] Farnell [16]). The filter was necessary to reduce the effects of the measurement system on the floating probe and allow the detection of high frequency (up to 500 kHz) plasma potential oscillations.…”

Section: Floating Emissive Probementioning

confidence: 99%

“…Although the amplitude of the potential oscillations was relatively small in the prototype NSTAR case compared with the open cathode case, the oscillations were included because they affect the widths of the IEDFs. The phase value, t phase , was set to zero based on time-varying, multiple-emissive-probe rake experiments [16], which showed only small variations of the potential oscillations with position in the NSTAR discharge chamber. The ions were binned according to energy and the particle weights were added to determine the relative strength of particles with different energies.…”

Section: Prototype Nstar Discharge Chamber Configuration-simulation R...mentioning

confidence: 99%

Comparison of hollow cathode discharge plasma configurations

Farnell

Williams

Farnell

2011

Plasma Sources Sci. Technol.

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Hollow cathodes are used in plasma contactor and electric propulsion devices to provide electrons for sustaining plasma discharges. Based on previous cathode life tests where erosion was observed on hollow cathode assembly components, it is desirable to understand the plasma flow field downstream of hollow cathodes. Plasma flow field measurements are presented herein for hollow cathode generated plasmas using both local and remotely located plasma diagnostics. Two cathode discharges are presented: 1) an open, no magnetic field configuration and 2) a setup simulating an ion thruster discharge chamber. In the open cathode configuration, large amplitude plasma potential oscillations, ranging from 20 V to 85 V within a 34 V discharge, were observed using a floating emissive probe. These oscillations were observed over a dc potential profile that contained a clear potential hill structure. A remotely located electrostatic analyzer (ESA) was used to measure the energy of ions produced within the plasma, and energies were detected that met and in some cases exceeded the peak plasma potentials detected by the emissive probe. In the prototype NSTAR-like discharge chamber configuration, plasma potentials from the emissive probe agreed with ion energies recorded by the remotely located ESA. A correlation model was used to compare the local and remote measurements in both cathode discharges. Nomenclature

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Magnetic filter type plasma source for ground-based simulation of low earth orbit environment

Rubin¹,

Farnell²,

Williams³

et al. 2009

Plasma Sources Sci. Technol.

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Simulation of the low Earth orbit (LEO) plasma environment in ground-based vacuum facilities is important for studies of spacecraft interaction with ionospheric plasmas. In this paper we describe the design and performance of a magnetic filter-equipped plasma source. Experimental data collected in the expanding plasma downstream of the source suggest it is a good candidate for use as a LEO plasma simulator in that the expanding plasma has a very low electron temperature and contains streaming ions-the plasma environment encountered by satellites in LEO. Adjustable plasma source operating conditions of flow rate, discharge current and discharge voltage enable production of plasma electron temperatures over the range from 0.17 to 0.35 eV and streaming ion energies over the range from 1 to 4 eV.

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Correlation of Direct and Remote Measurements on a Hollow Cathode Plasma Discharge

Cited by 4 publications

References 1 publication

Single particle simulations of electron transport in the near-field of Hall thrusters

Single particle simulations of electron transport in the near-field of Hall thrusters

Comparison of hollow cathode discharge plasma configurations

Magnetic filter type plasma source for ground-based simulation of low earth orbit environment

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