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Electron Transport in
Hall Thrusters
Winston FriasGraduate Student
University of Saskatchewan
May 9 2012
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Outline of the talk
I. Hall ThrustersII. Electron Transport in Hall ThrustersIII. Future Work
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I. HallThrusters
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Introduction
- Hall thrusters are electrostatic coaxial plasma accelerators.- Developed and successfully operated in USSR from 1960s
(>240 missions), SPT100 last decade used in USA andEurope.
- Main features:
- High specific impulse,- High efficiency,- Low thrust.
- Well suited for station keeping and orbit transfer.- Two main types:
- Stationary plasma thruster (SPT),- Thruster with anode layer (TAL).
- SPT most common and best studied configuration.
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Hall Thrusters
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Hall Thruster
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Propellant Xe
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Current Issues in Hall Thruster Research
- Hall thruster applications are expanding. New requirementson
reliability , performance, lifespan, efficiency, etc.
- New and more sophisticated computer codes to simulateHall thrusters.
Fluid, fully kinetic, hybrid or PIC codes.
- Major physics problem has not been resolved: How toexplain and predictanomalously large electron current
- Plasma fluctuations. Fundamental problem - plasmaturbulence induced electron transport- Near wall conductivity (enhanced collisions with the
walls)
- Problems common to other devices e.g. magnetron
discharges, PIII. 77
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II. ElectronTransport
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Classical Electron Transport inAbsence of Magnetic Fields
- Steady-state and large collision frequency assumed.
- Fluid Equation
- Solve for v assuming isothermal plasma to obtain
- The mobility and diffusion coefficients are then given by:
- Related via Einstein relation
Mobility Diffusion
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Classical Electron Transport inPresence of Magnetic Fields
- Particle is magnetized if undergoes many gyrations beforecolliding. Its Hall parameter is high
- Solve for electron velocity:
LargeHallParameter
Mobilityproportional to 1/B2
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electron
collision
E B drift(azimuthal)
E
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Fluctuation Induced Transport- Instabilities give rise to transport.- Using continuity equation, perturbed density and velocity for
ions and electrons can be obtained. The time average isgiven by
- Current has two contributions:
Fluctuating current. Time averagenot zero due to relative phasedifference, even when timeaverage of the individualperturbations is zero. Notpredicted by classical theory.
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Characterized by effectiveHallParameter
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Near Wall ConductivityElectron collisions with the wall lead to decorrelation of
particle motion and enhanced transport
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- Proposed byMorozov
- Channel width