Bulletin of the American Physical Society
65th Annual Gaseous Electronics Conference
Volume 57, Number 8
Monday–Friday, October 22–26, 2012; Austin, Texas
Session RR3: Plasma Propulsion II |
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Chair: John Foster, University of Michigan Room: Classroom 202 |
Thursday, October 25, 2012 1:30PM - 2:00PM |
RR3.00001: Rotating spoke phenomena in low pressure E $\times $ B discharges Invited Speaker: Yevgeny Raitses The rotating spoke is azimuthal plasma non-uniformity which has been observed in a variety of low pressure cross-field discharges of cylindrical geometry [1-3]. The spoke can appear in different modes ranging from m=1 to higher order modes which propagate in the direction perpendicular to electric and magnetic fields with velocities of much lower than E$\times $B velocity [2,3]. Although spoke phenomena is known for more than four decades, physical mechanism responsible for triggering of the spoke is still not understood. Recent studies of Hall thrusters and Penning-type magnetized plasma discharges demonstrated that the spoke is directly responsible for the enhancement of the electron cross-field transport in these devices [1,4]. A combination of time-resolving plasma measurements, including high speed imaging and probes suggest that for partially ionized magnetized plasma discharges, the spoke instability is triggered by ionization mechanism [4]. These experimental results are supported by recent particle-in-cell simulations. The advancement in understanding of the spoke mechanism enabled us to develop and demonstrate effective methods of spoke control, including mode, velocity and direction of the spoke, and spoke suppression [5]. Among practical implications of these results is the ability to develop more effective methods of plasma confinement and uniformity for magnetically-enhanced discharges and more efficient magnetized plasma thrusters. In collaboration with M. Griswold, L. Ellison, N. J. Fisch, K. Matyash, R. Schneider and A. Smolyakov.\\[4pt] [1] S. Jaeger, Th. Pierre, C. Rebont, Phys. Plasmas 16, 022304 (2009)\\[0pt] [2] J. B. Parker, Y. Raitses, N. J. Fisch, Appl. Phys. Lett. 97, 091501 (2010)\\[0pt] [3] M. S. McDonald, A. D. Gallimore, IEEE Trans. Plasma Sci. 39, 2952 (2011)\\[0pt] [4] C. L. Ellison, Y. Raitses, N. J. Fisch, Phys. Plasmas 19, 013503 (2012)\\[0pt] [5] M. E. Griswold, C. L. Ellison, Y. Raitses, N. J. Fisch, Phys. Plasmas 19, 053506 (2012). [Preview Abstract] |
Thursday, October 25, 2012 2:00PM - 2:15PM |
RR3.00002: Performance characterization of a permanent-magnet helicon plasma thruster Kazunori Takahashi, Christine Charles, Rod Boswell Helicon plasma thrusters operated at a few kWs of rf power is an active area of an international research. Recent experiments have clarified part of the thrust-generation mechanisms. Thrust components which have been identified include an electron pressure inside the source region and a Lorentz force due to an electron diamagnetic drift current and a radial component of the applied magnetic field. The use of permanent magnets (PMs) instead of solenoids is one of the solutions for improving the thruster efficiency because it does not require electricity for the magnetic nozzle formation. Here the thrust imparted from a permanent-magnet helicon plasma thruster is directly measured using a pendulum thrust balance. The source consists of permanent magnet (PM) arrays, a double turn rf loop antenna powered by a 13.56 MHz rf generator and a glass source tube. The PM arrays provide a magnetic nozzle near the open exit of the source and two configurations, which have maximum field strengths of about 100 and 270 G, are tested. A thrust of 15 mN, specific impulse of 2000 sec and a thrust efficiency of 8 percent are presently obtained for 2 kW of input power, 24 sccm flow rate of argon and the stronger magnetic field configuration. [Preview Abstract] |
Thursday, October 25, 2012 2:15PM - 2:30PM |
RR3.00003: Collective Thomson scattering investigations of the Hall thruster plasma Sedina Tsikata, Cyrille Honore, Dominique Gresillon, Nicolas Lemoine, Jordan Cavalier Anomalous electron transport outside the Hall thruster channel is believed to be due to plasma turbulence. Recent experiments using a specially-designed collective Thomson scattering diagnostic on a 5kW thruster have permitted the identification of a wave believed to be involved in transport. The observed properties of the mode, which is naturally driven by the fast azimuthal electron drift, are in line with predictions from PIC simulations and linear kinetic theory analysis. Detailed characterizations of mode properties, including dispersion relation, directivity, spatial extent and fluctuation amplitude have been obtained. These studies are now extended to consider the universality of mode features in a 200W permanent magnet Hall thruster and links between thruster performance, operating r\'egimes and the presence of such a mode. [Preview Abstract] |
Thursday, October 25, 2012 2:30PM - 2:45PM |
RR3.00004: Effect of applied magnetic nozzle on an MPD Thruster Akira Ando, Yuki Izawa, Kohei Okawa, Yoko Hashima, Hiroshi Watanabe, Nozomi Tanaka Electric propulsion systems are suitable for long-term mission in space due to its higher specific impulse. An Magneto-Plasma-Dynamic Thruster (MPDT) is one of the promising thrusters of high power electric propulsion systems. It has been reported that the thrust performance of an MPDT can be improved by applying an axial magnetic field on it. In order to investigate the effect of applied field on an MPDT, we have investigated plume plasma parameters and thrust performance in an applied field MPDT. Different types of divergent magnetic nozzle were applied to an MPDT, and thrust was measured using a pendulum type thrust target. Experiments were performed with hydrogen, helium, and argon as propellant gas. Thrust increased with a discharge current up to 6kA and applied magnetic field up to 0.4T. Maximum thrust of 7N was obtained when the peak position of the applied magnetic field was set upstream of the muzzle of the MPDT. The highest thrust performance was obtained with hydrogen gas with divergent magnetic nozzle applied to the MPDT. [Preview Abstract] |
Thursday, October 25, 2012 2:45PM - 3:00PM |
RR3.00005: VASIMR VX-200 thruster throttling optimization from 30 to 200 kW Jared Squire, Chris Olsen, Franklin Chang-Diaz, Benjamin Longmier, Maxwell Ballenger, Mark Carter, Tim Glover, Greg McCaskill The VASIMR$^{\mbox{{\textregistered}}}$ VX-200 experimental plasma thruster incorporates a 40 kW helicon plasma source with a 180 kW Ion Cyclotron Heating (ICH) acceleration stage integrated in a superconducting magnet. Argon propellant mass flow is injected up to 140 mg/s. Rapid plasma start up ($<$ 100 ms) and high pumping speed ($>$ 10$^{5}$ liters/s) in a 150 m$^{3}$ vacuum chamber achieve performance measurements with the charge exchange mean-free-path greater than 1 m in the background neutral gas (pressure $<$ 10$^{-5}$ Torr). The thruster efficiency at 200 kW total power is 72 $\pm $ 9{\%}, the ratio of effective jet power to input RF power, with an Isp = 4900 $\pm $ 300 seconds (flow velocity of 49 km/s), and an ion flux of 1.7 $\pm $ 0.1 $\times $ 10$^{21}$/s. The thrust increases steadily with power to 5.8 $\pm $ 0.4 N until the power is maximized and there is no indication of saturation. The plasma density near the device exit exceeds 10$^{18}$ m$^{-3}$ with a power density over 5 MW/m$^{2}$. An extensive study of thruster performance, efficiency and thrust-to-power ratio, as a function of Ar propellant flow rate and ICH-to-helicon RF power ratio has been carried out over a total power range of 30 to 200 kW. Optimized throttling set points are determined. The experimental configuration and results of this study are presented. [Preview Abstract] |
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