A5080429889- Plasma Diagnostics and Applications
- Electrohydrodynamics and Fluid Dynamics
- Magnetic confinement fusion research
- Plasma Applications and Diagnostics
- Magnetic Field Sensors Techniques
- Laser-induced spectroscopy and plasma
- Ionosphere and magnetosphere dynamics
- Particle accelerators and beam dynamics
- Advanced Data Storage Technologies
- Dust and Plasma Wave Phenomena
- Vacuum and Plasma Arcs
- Radiation Effects in Electronics
- Metal and Thin Film Mechanics
- Astro and Planetary Science
- Planetary Science and Exploration
- Atomic and Molecular Physics
- Muon and positron interactions and applications
- Diamond and Carbon-based Materials Research
- Electrostatic Discharge in Electronics
- Gas Dynamics and Kinetic Theory
- Fusion materials and technologies
- Aerosol Filtration and Electrostatic Precipitation
- Particle Dynamics in Fluid Flows
- Solar and Space Plasma Dynamics
- Laser-Plasma Interactions and Diagnostics
Jet Propulsion Laboratory
2016-2025
California Institute of Technology
2004-2017
Science Applications International Corporation (United States)
2001-2004
The Ohio State University
1998-2001
We demonstrate a technique by which erosion of the acceleration channel in Hall thrusters can be reduced at least few orders magnitude. The first principles technique, now known as “magnetic shielding,” have been derived based on findings 2-D numerical simulations. simulations, turn, guided modification an existing 6-kW laboratory thruster to test theory and are main subject this Part I article. II expands results experiments. Near walls magnetically shielded (MS) experiment agree that (1)...
In a qualification life test of Hall thruster it was found that the erosion acceleration channel practically stopped after ∼5600 h. Numerical simulations using two-dimensional axisymmetric plasma solver with magnetic field-aligned mesh reveal when receded from its early-in-life to steady-state configuration following changes occurred near wall: (1) reduction electric field parallel wall prohibited ions acquiring significant impact kinetic energy before entering sheath, (2) potential fall in...
The physics of magnetic shielding in Hall thrusters were validated through laboratory experiments demonstrating essentially erosionless, high-performance operation. field near the walls a thruster was modified to effectively eliminate wall erosion while maintaining topology away from necessary retain efficient Plasma measurements at validate our understanding as derived theory. plasma potential maintained very anode potential, electron temperature reduced by factor two three, and ion current...
This paper provides perspectives on recent progress in the understanding of physics devices where external magnetic field is applied perpendicularly to discharge current. configuration generates a strong electric field, which acts accelerates ions. The many applications this set up include generation thrust for spacecraft propulsion and separation species plasma mass devices. These ExB plasmas are subject plasma-wall interaction effects as well various micro macro instabilities, devices, we...
The ionized gas in Hall-effect plasma accelerators spans a wide range of spatial and temporal scales, exhibits diverse physics some which remain elusive even after decades research. Inside the acceleration channel quasiradial applied magnetic field impedes current electrons perpendicular to it favor significant component E×B direction. Ions are unmagnetized and, arguably, collisional mean free paths. Collisions between atomic species rare. This paper reports on computational approach that...
We demonstrate by numerical simulations and experiments that the unmagnetized ion beam formed in a Hall thruster can be controlled an applied magnetic field manner reduces 2–3 orders of magnitude deleterious bombardment containing walls. The suppression wall erosion thrusters to such low levels has remained elusive for decades.
The temporal fluctuations in the near plume of a 100-A LaB(6) hollow cathode are experimentally investigated. A probe array is employed to measure amplitude and dispersion axial modes plume, these properties examined parametrically as function operating conditions. onset ion acoustic turbulence observed at high current characterized by power spectrum that exhibits cutoff low frequency an inverse dependence on values. found decrease with flow rate but depend nonmonotonically discharge...
Hollow cathode plasma discharges are a fundamental part of large variety applications in industry, academia, and space. From surface processing coatings deposition to plasma–surface interaction research electric propulsion, advances hollow modeling performance critically important the progress evolution these other areas technology. This paper describes perspectives on that has been made recent years capabilities cathodes used discharges. While many developments have driven by demanding...
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Despite their long history and wide range of applicability that includes electric propulsion, detailed understanding the driving physics inside orificed hollow cathodes remains elusive. The theoretical complexity associated with multicomponent fluid cathode, difficulty accessing empirically this region, have limited our ability to design perform better last longer. A two-dimensional axisymmetric model multispecies an cathode is presented. level detail attained by allowed its extended system...
Ions with energies significantly in excess of the applied discharge voltage have been reported for many years hollow cathode discharges. Models dc potential hills downstream and instabilities postulated double layers orifice proposed to explain this, but not substantiated. Measurements rf plasma density profiles near exit cathodes by miniature fast-scanning probes suggests that turbulent ion acoustic fluctuations ionization plume increase energy ions flow from this region. Increases current...
A detailed study of the spatial variation plasma density, temperature, and potential in hollow cathodes using miniature fast scanning probes has been undertaken order to better understand cathode operation provide benchmark data for modeling performance life described a companion paper. Profiles are obtained throughout discharge very high-density orifice region by pneumatically driven Langmuir probes, which inserted directly into from either upstream insert inside or downstream anode-plasma...
The wear of the keeper electrode in discharge hollow cathodes is a major impediment to implementation ion propulsion onboard long-duration space science missions. development predictive theoretical model for cathode life has long been sought, but its realization hindered by complexities associated with physics partially ionized gas and erosion mechanisms these devices. Thus, although several have hypothesized, quantitative explanation test profiles remained incomplete. A two-dimensional...
Magnetic shielding in Hall thrusters significantly reduces the transport of high-energy ions to channel walls such that erosion is effectively eliminated. The physics magnetic were validated through laboratory experiments demonstrating essentially erosionless, high-performance thruster operation for first time. field near a was modified enable while maintaining topology away from necessary retain efficient operation. Sixteen diagnostics deployed assess performance, thermal, stability, and...
Measurements, simplified analyses, and two-dimensional numerical simulations with a fluid plasma model show that classical resistivity cannot account for the elevated electron temperatures steep potential gradients measured in 25–27.5A electric propulsion hollow cathode. The cathode consisted of 1.5cm tube an ∼0.28cm diameter orifice was operated 5.5SCCM (SCCM denotes cubic centimeter per minute at STP) xenon flow using two different anode geometries: segmented cone circular flat plate....
The cross-field electron mobility in Hall thrusters is known to be enhanced by wall collisionality and turbulent plasma fluctuations. Although progress has been made understanding the plasma-wall interaction instabilities responsible for anomalous transport, a predictive model based on underlying physics of these processes yet emerge. Hybrid-PIC simulations thruster have typically depended semi-empirical models provide sufficient current match experimental results. These are capable...
Upon the completion of two long-duration life tests a 30-cm ion engine, orifice channel neutralizer hollow cathode was eroded away to as much twice its original diameter. Whereas opened significantly, no noticeable erosion discharge observed. Noquantitative explanation these trends has been established since tests. A two-dimensional model partially ionized gas inside devices developed and applied cathode. The numerical simulations show that main mechanism responsible for is sputtering by...
In a Qualification Life Test (QLT) of the BPT-4000 Hall thruster that recently accumulated >10,000 h it was found erosion acceleration channel practically stopped after ~5,600 h. Numerical simulations this using 2-D axisymmetric, magnetic field-aligned-mesh (MFAM) plasma solver reveal process led to significant reduction multifaceted. It is when receded from its early-in-life geometry steady-state configuration several changes in near-wall and sheath were induced by field that, collectively,...
The successful application of a fully shielding magnetic field topology in low-power Hall thruster is demonstrated through the testing MaSMi-60 (an improved variant original Magnetically Shielded Miniature thruster). device was operated at discharge powers from 160 to 750 W voltages ranging 200 400 V. Several techniques were used determine effectiveness achieved by and estimate reduction channel erosion rate enabled topology. This ultimately suggested an improvement life factor least 10...
Since the inception of Hall-effect thruster more than five decades ago, many theories have been proposed about source(s) anomalous cross-field transport that is known to occur in these devices. Yet, none has implemented two-dimensional (2D) (r–z) simulations and successfully predicted behavior discharge erosion a over different operating conditions geometries. We present results from numerical experiments with 2D axisymmetric hydrodynamics code show plasma solution relatively insensitive...
Magnetic shielding of Hall thrusters has been shown to reduce erosion the channel walls by at least a few orders magnitude, thereby enabling use these devices in deep space missions. Wear tests magnetically shielded thrusters, such as H6 and HERMeS, have revealed that some sputtering occurs surface inner pole, phenomenon not observed unshielded thrusters. Even though rates measured pole during ground testing are typically an order magnitude lower than those found acceleration it is critical...
In a proof-of-principle effort to demonstrate the feasibility of magnetically shielded (MS) Hall thrusters, an existing laboratory thruster has been modified with guidance physics-based numerical simulation. When operated at discharge power 6-kilowatts designed reduce total energy and flux ions channel insulators by greater than 1 3 orders magnitude, respectively. The erosion rates in this MS configuration are predicted be least 2-4 magnitude lower those baseline (BL) configuration. At such...