Search

The performance of a three-channel, 100-kW nested Hall thruster was evaluated on xenon propellant for total powers up to 102 kW. The thruster demonstrated stable operation in all seven available ch...

The plasma plume properties of a three-channel 100-kW-class nested Hall thruster were measured on xenon propellant for total powers up to 80 kW. The thruster was throttled through all seven availab...

A high-power nested Hall thruster was operated with cathode flow fractions from 7 to 3% of the total anode flow rate in a two-channel operating configuration at 27 kW total discharge power. The thr...

An overview of low temperature, partially magnetized ion sources is presented. This class of devices is broadly characterized by plasma densities below 1019 m−3, electron temperatures below 100 eV, and magnetic field strength tailored such that electrons are magnetized whereas ions are not. The overarching approach is pedagogical, targeting an audience that does not necessarily have an expertise in low temperature devices. A tutorial is presented on the basic physics of operation of common ion sources including an overview of standard methods for plasma generation and acceleration. Typical diagnostics and common uses of these plasma sources are also reviewed. Special attention is given to applications in plasma propulsion and materials processing. This class of ion sources is then discussed in the context of the current state of the field, key technical and scientific challenges, and future prospects.

Eagle Harbor Technologies, Inc. (EHT) and the University of Michigan (UM) made the first direct performance measurement of a continuously operating Rotating Magnetic Field (RMF) – Field-Reversed Configuration (FRC) Thruster using a standard inverted-pendulum thrust stand in space-like conditions. EHT developed the power system, and UM constructed the RMF-FRC thruster and conducted measurements in their Large Vacuum Test Facility.

International audience; This paper provides perspectives on recent progress in understanding the physics of devices in which the external magnetic field is applied perpendicular to the discharge current. This configuration generates a strong electric field that acts to accelerate ions. The many applications of this set up include generation of thrust for spacecraft propulsion and separation of species in plasma mass separation devices. These “E × B” plasmas are subject to plasma–wall interaction effects and to various micro- and macroinstabilities. In many devices we also observe the emergence of anomalous transport. This perspective presents the current understanding of the physics of these phenomena and state-of-the-art computational results, identifies critical questions, and suggests directions for future research.

An experimental investigation into the correlation between ion acoustic turbulence (IAT) and anomalous ion heating in the plume of a 100 A-class LaB6 hollow cathode is presented. Laser-induced fluo...

A mathematical model of the ion–acoustic turbulence that is known to develop in the plume of hollow cathodes is presented. The model takes the form of a partial differential equation for the ion–ac...

The performance of a 9-kW class magnetically shielded Hall thruster operating on xenon and krypton propellants is experimentally characterized. Thrust and efficiency measurements performed at discharge powers ranging from 4.5 to 9 kW indicate that the anode efficiency of krypton is 9%–18% lower than that of xenon. This difference is comparable to previous measurements reported for unshielded Hall thrusters, although it is found that unlike in previous studies, the efficiency ratio widens with increasing discharge voltage. Far-field probes are employed to measure the contributions to anode efficiency at conditions of 4.5 and 6 kW. These results indicate that mass utilization has the largest impact on the difference in performance between xenon and krypton. Assuming this mass utilization remains the dominant driver at higher voltages, it is proposed that the higher electron temperature of shielded thrusters along channel centerline coupled with the nonlinearity of the ionization cross section may explain why the efficiency gap widens with increasing voltage for shielded thrusters. The results are discussed in the context of optimizing magnetically shielded Hall thrusters for improved performance on krypton propellant.

The dynamic properties of the Hall thruster breathing mode are investigated experimentally. Non-invasive time-resolved laser diagnostics are combined with a quasi-one-dimensional non-Maxwellian modeling technique to yield the high-speed evolution of a variety of plasma properties over the course of a breathing oscillation. The fluctuations of both ion and neutral densities are quantified in terms of amplitude and dispersion and are interpreted in the context of a simplified dispersion relation. It is found that the oscillations associated with the breathing mode are likely ion and neutral waves propagating with phase velocities commensurate with the local species drift speed. Further, the amplitudes of the waves are shown to decay with distance from the anode. This effect can be explained largely by the influence of the expansion of the background plasma and neutral gas. This monotonic decay combined with the downstream propagating nature of the waves suggests that these oscillations are influenced by conditions upstream of the acceleration and ionization regions. By comparing the presence of these waves to inferred electron temperature fluctuations, the hypothesis that the breathing mode is governed by a process in which the modulation of the neutral density near the anode sheath or the anode itself is coupled to a downstream ionization instability is qualitatively explored. The possibility of these waves relating to cyclical recombination of ions at the anode is also discussed.

The XR-100 team successfully completed high power system testing of a Nested Hall Thruster system made up of the X3 Nested Hall Thruster, a modular Power Processing Unit, and a 5 valve Mass Flow Controller as the culmination of work performed under a NASA NextSTEP program. The test campaign attained several key firsts, including highest directly measured thrust of an electric propulsion (EP) string, highest demonstrated current of an EP string, and highest power operation of an EP string at thermal equilibrium published to date. Most importantly, the XR-100 system testing demonstrated that a 100 kW-class Nested Hall Thruster system has comparable performance and behavior to current state-of-the-art mid power Hall Thrusters, validating that the heritage technology can be scaled up to 100+ kW

Electric thrusters are finding increasing usage worldwide in spacecraft applications. Significant progress has been made in recent years in the modeling and performance of thermionic hollow cathodes used in flight thrusters, such as Hall and ion thrusters, or other types of plasma sources, such as for technological plasmas. The recent progress is surveyed in this paper through the discussion of six areas: hollow cathode modeling and simulation, low-current hollow cathodes, high-current hollow cathodes, heaterless hollow cathodes, new thermionic insert materials, and plasma oscillations. This includes descriptions of hollow cathode designs capable of