Bulletin of the American Physical Society
65th Annual Gaseous Electronics Conference
Volume 57, Number 8
Monday–Friday, October 22–26, 2012; Austin, Texas
Session LW3: Plasma Propulsion I |
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Chair: Rod Boswell, Australian National University Room: Classroom 202 |
Wednesday, October 24, 2012 1:30PM - 1:45PM |
LW3.00001: A continuous dual ion beam formed by successive acceleration of positive and negative ions Ane Aanesland, Lara Popelier, Denis Renaud, Pascal Chabert The distinctive feature of the PEGASES thruster is that both positive and negative ions are accelerated to provide thrust such that an additional neutralization system is redundant; the accelerated product provides the space charge and current neutralization of the beam. The first proof-of concept of the alternate acceleration has recently been achieved. The ions are accelerated from an ion-ion plasma by a set of grids where the grid in contact with the plasma is biased with square voltage waveforms with frequencies in the kHz range and voltages less $\pm$500~V. Time resolved measurements show that the positive and negative ions are extracted at the positive and negative bias period, respectively, producing a continuous beam of ions. For positive ions, the beam energy corresponds to the sum of the applied acceleration voltage and the plasma potential. For negative ions, the beam energy is lower than the applied voltage and depends on the applied bias frequency. The effects of the voltage waveform and the grid surface condition on the resulting beams are discussed. [Preview Abstract] |
Wednesday, October 24, 2012 1:45PM - 2:00PM |
LW3.00002: Implementation of a polytropic model for two-dimensional hybrid Hall thruster simulations Eunsun Cha, Eduardo Fernandez, Mark Cappelli A polytropic model for Hall discharge simulations is developed and tested against data for a laboratory Hall thruster. 2-D hybrid particle-in-cell (PIC) simulations, widely used to describe plasma properties of Hall thrusters, solve the electron energy equation for electron temperature requiring electron mobility as a specified parameter. Motivated by experiments that suggest a simpler polytropic relation between the electron density and electron temperature, we have adopted a 2-D hybrid-PIC to use this relationship as a means of relaxing the need to specify the electron mobility. By removing the usual ad-hoc assumptions of the form of the electron mobility, the polytropic model, if transportable to other operating conditions and Hall thruster designs, can be a powerful performance estimator and optimization tool. In this presentation, we discuss the implementation of this model and early results. [Preview Abstract] |
Wednesday, October 24, 2012 2:00PM - 2:15PM |
LW3.00003: Experimental Assessment of Plasma Transport in a 16-cm Multicusp Device Aimee Hubble, John Foster The physics of plasma transport from the bulk plasma through the magnetic cusp to the anode remains poorly understood. A proper accounting of plasma losses to the anode is critical to accurate modeling of multicusp device performance. In this work, plasma transport in a 16-cm multicusp discharge chamber was studied. Each ring was covered with an electrically isolated electrode, which enables the direct measurement of current to each individual ring as well as the discharge chamber wall. A translatable Langmuir probe was used to obtain maps of spatially resolved plasma parameters in bulk plasma region. These maps of spatially resolved plasma density, electron temperature, and plasma potential were compared to current collection at the cusps as well as the magnetic circuit and device performance. Ring electrode measurements coupled with spatially resolved plasma parameter measurements throughout the discharge chamber allow for an assessment of plasma losses to each ring in terms of an ``effective loss area'' which, multiplied by electron current density incident on the bulk/cusp boundary, gives the correct collected current to each ring. A relationship between effective loss area and the physical loss area was determined that can be applied to a 0-D particle and energy balance model. [Preview Abstract] |
Wednesday, October 24, 2012 2:15PM - 2:30PM |
LW3.00004: Electron Transport via Collisional Mechanisms in a Cusped Plasma Ion Accelerator Christopher Young, Mark Cappelli A plasma accelerator with applications to low power space propulsion (below 200 W) is experimentally and computationally investigated. Such devices efficiently ionize propellant by trapping electrons between strong adjacent magnetic cusps. Electron transport and ionization processes in this class of plasma accelerator are still poorly understood. A numerical model built around experimental plasma potential measurements of the device is presented, in which single test electron trajectories are traced throughout the simulation domain. A mixture of classical and anomalous collisional processes (respectively linked to the local neutral propellant density and magnetic field strength - Bohm diffusion) is required to recover the behavior observed in laboratory experiments. [Preview Abstract] |
Wednesday, October 24, 2012 2:30PM - 2:45PM |
LW3.00005: Time evolution of the EEDF in the plasma plume of a Hall thruster Stephane Mazouffre, Kaethe Dannenmayer, Pavel Kudrna, Milan Tichy A Hall thruster (HT) is one type of electric engine currently in use onboard geosynchronous satellites and scientific space probes. In a HT, the electric field at the origin of ion acceleration is generated in a low-pressure magnetized discharge in cross-field configuration. As no grid are employed for beam formation, such a thruster is not current limited and a relatively large thrust, in comparison with gridded ion engines, is achieved, which makes this technology of great interest for orbit transfer maneuvers and deep-space exploration missions. One important issue in the field of electric propulsion is the interaction between the host spacecraft and the plasma plume. Up to now, a large amount of studies has been performed on ion flow properties. Recently we carried out time-averaged measurements of the electron properties in a HT plume by means of Langmuir probe. The goal was to provide accurate data for validation of plume numerical simulations. Nevertheless, as the discharge of a HT is highly non stationary, it appeared necessary to turn to time-resolved measurements. In this contribution we present measurements of the time-varying EEDF at a microsecond time-scale in the plasma plume of two HTs of different sizes and power levels. [Preview Abstract] |
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