Bulletin of the American Physical Society
69th Annual Gaseous Electronics Conference
Volume 61, Number 9
Monday–Friday, October 10–14, 2016; Bochum, Germany
Session JW4: Plasma Propulsion and Aerospace Applications II |
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Chair: Christine Charles, Australian National University Room: 3 |
Wednesday, October 12, 2016 8:30AM - 8:45AM |
JW4.00001: Plume properties measurement of an Electron Cyclotron Resonance Accelerator Sara Correyero, Theo Vialis, Julien Jarrige, Denis Packan Some emergent technologies for Electric Propulsion, such as the Electron Cyclotron Resonance Accelerator (ECRA), include magnetic nozzles to guide and expand the plasma. The advantages of this concept are well known: wall-plasma contact is avoided, it provides a current-free plume, it can allow to control thrust by modifying the magnetic field geometry, etc. However, their industrial application requires the understanding of the physical mechanisms involved, such as the electron thermodynamics at the plasma plume expansion, which is crucial to determine propulsive performances. \\ This work presents a detailed characterization of the plasma plume axial profile in an ECR plasma thruster developed at ONERA. Langmuir, emissive, Faraday and ion energy probes are used to measure the electric potential space evolution, the current and electron energy distribution function in the plume, from the near field to the far field. \\ The experimental results are compared with a quasi-1D (paraxial) steady-state kinetic model of a quasineutral collisionless magnetized plasma which is able to determine consistently the axial evolution of the electric potential and the electron and ion distribution functions with their associated properties. [Preview Abstract] |
Wednesday, October 12, 2016 8:45AM - 9:00AM |
JW4.00002: A Coupled MHD and Thermal Model Including Electrostatic Sheath for Magnetoplasmadynamic Thruster Simulation Akira Kawasaki, Kenichi Kubota, Ikkoh Funaki, Yoshihiro Okuno Steady-state and self-field magnetoplasmadynamic (MPD) thruster, which utilizes high-intensity direct-current (DC) discharge, is one of the prospective candidates of future high-power electric propulsion devices. In order to accurately assess the thrust performance and the electrode temperature, input electric power and wall heat flux must correctly be evaluated where electrostatic sheaths formed in close proximity of the electrodes affect these quantities. Conventional model simulates only plasma flows occurring in MPD thrusters with the absence of electrostatic sheath consideration. Therefore, this study extends the conventional model to a coupled magnetohydrodynamic (MHD) and thermal model by incorporating the phenomena relevant to the electrostatic sheaths. The sheaths are implemented as boundary condition of the MHD model on the walls. This model simulated the operation of the 100-kW-class thruster at discharge current ranging from 6 to 10 kA with argon propellant. The extended model reproduced the discharge voltages and wall heat load which are consistent with past experimental results. In addition, the simulation results indicated that cathode sheath voltages account for approximately 5–7 V subject to approximately 20 V of discharge voltages applied between the electrodes. [Preview Abstract] |
Wednesday, October 12, 2016 9:00AM - 9:15AM |
JW4.00003: Characterization of an electrodeless ECR plasma thruster Théo Vialis, Julien Jarrige, Denis Packan Several advanced plasma thruster technologies are currently being studied for the 1-10 $mN$ range. ONERA is developing an Electron Cyclotron Resonance (ECR) plasma thruster, whose main advantage is to produce a current-free plume. It does not need a neutralizing cathode, which is one of the most fragile component in electrostatic thrusters. The ECR thruster consists of a coaxial structure immersed in an axial divergent magnetic field, fed with xenon. A plasma is generated by resonant absorption of microwave power (at 2.45 GHz) and is accelerated in an electron driven magnetic nozzle to produce the thrust. Previous measurements, performed with electrostatic probes, have shown promising performances. Electrons are heated at very high temperatures (several tens of eV), and ion kinetic energy is up to 400 $eV$ in the plume. The estimated thrust is 1 $mN$, with an efficiency of 16%, for a power of 30W. In this work, a new version of the device has been conceived for direct thrust measurement on a dedicated thrust balance. The effect of magnetic field topology, propellant, mass flow rate and absorbed power are investigated. Thrust measurement are compared with values estimated from electrostatic probes results (ion current and energy). [Preview Abstract] |
Wednesday, October 12, 2016 9:15AM - 9:30AM |
JW4.00004: Theory for the anomalous electron transport in Hall-effect thrusters Trevor Lafleur, Scott Baalrud, Pascal Chabert Using insights from particle-in-cell (PIC) simulations, we develop a kinetic theory to explain the anomalous cross-field electron transport in Hall-effect thrusters (HETs). The large axial electric field in the acceleration region of HETs, together with the radially applied magnetic field, causes electrons to drift in the azimuthal direction with a very high velocity. This drives an electron cyclotron instability that produces large amplitude oscillations in the plasma density and azimuthal electric field, and which is convected downstream due to the large axial ion drift velocity. The frequency and wavelength of the instability are of the order of 5 MHz and 1 mm respectively, while the electric field amplitude can be of a similar magnitude to axial electric field itself. The instability leads to enhanced electron scattering many orders of magnitude higher than that from standard electron-neutral or electron-ion Coulomb collisions, and gives electron mobilities in good agreement with experiment. Since the instability is a strong function of almost all plasma properties, the mobility cannot in general be fitted with simple 1/B or 1/B$^{\mathrm{2}}$ scaling laws, and changes to the secondary electron emission coefficient of the HET channel walls are expected to play a role in the evolution of the instability. [Preview Abstract] |
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