What We Have Learned By Studying The P5 Hall Thruster

The Hall thruster is an advanced spacecraft propulsion system that uses electrical power provided by the spacecraft to generate thrust by ionizing and accelerating ions to high velocities. While Hall thrusters have been tested in laboratories for nearly forty years and first flew in space some thirty years ago, little is known about the plasma within these devices. This lack of knowledge has led to the expensive trial‐and‐error approach practiced in Hall thruster development over the years. The difficulty in collecting interior plasma data stems from the intense heat flux a probe receives. While optical measurements can give some information about the plasma, probes provide data about the plasma that are not accessible with optical approaches. Discharge channel plasma data are vital for extending our understanding of Hall thruster physical processes, for validating thruster models, and for developing advanced, next‐generation engines for high ΔV missions. The paper summarizes the results of research aimed at using probes to characterize the internal plasma structure of a laboratory Hall thruster developed specifically for this purpose. Internal plasma parameter measurements were accomplished by using the unique High‐speed Axial Reciprocating Probe (HARP) system, which enabled, for the first time, the insertion and removal of probes from the Hall thruster discharge channel while minimizing perturbation to thruster operation. The system was used with an emissive probe to map plasma potential, and a double Langmuir probe to map electron temperature and ion number density. Thruster perturbation, determined by monitoring discharge current, was less than 10% for the majority of measurements. © 2003 American Institute of PhysicsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87932/2/533_1.pd

A Preliminary Investigation of Hall Thruster Technology

A three-year, NASA/BMDO-sponsored experimental program to conduct performance and plume plasma property measurements on two Russian Stationary Plasma Thrusters (SPTs) has been completed. The program utilized experimental facilitates at the University of Michigan's Plasmadynamics and Electric Propulsion Laboratory (PEPL). The main features of the proposed effort were as follows: We Characterized Hall thruster [and arcjet] performance by measuring ion exhaust velocity with probes at various thruster conditions. Used a variety of probe diagnostics in the thruster plume to measure plasma properties and flow properties including T(sub e) and n(sub e), ion current density and ion energy distribution, and electric fields by mapping plasma potential. Used emission spectroscopy to identify species within the plume and to measure electron temperatures

Monoclinic and triclinic phases in higher-order Devonshire theory

Devonshire theory provides a successful phenomenological description of many cubic perovskite ferroelectrics such as BaTiO3 via a sixth-order expansion of the free energy in the polar order parameter. However, the recent discovery of a novel monoclinic ferroelectric phase in the PZT system by Noheda et al. (Appl. Phys. Lett. 74, 2059 (1999)) poses a challenge to this theory. Here, we confirm that the sixth-order Devonshire theory cannot support a monoclinic phase, and consider extensions of the theory to higher orders. We show that an eighth-order theory allows for three kinds of equilibrium phases in which the polarization is confined not to a symmetry axis but to a symmetry plane. One of these phases provides a natural description of the newly observed monoclinic phase. Moreover, the theory makes testable predictions about the nature of the phase boundaries between monoclinic, tetragonal, and rhombohedral phases. A ferroelectric phase of the lowest (triclinic) symmetry type, in which the polarization is not constrained by symmetry, does not emerge until the Devonshire theory is carried to twelfth order. A topological analysis of the critical points of the free-energy surface facilitates the discussion of the phase transition sequences.Comment: 10 pages, with 5 postscript figures embedded. Uses REVTEX and epsf macros. Also available at http://www.physics.rutgers.edu/~dhv/preprints/dv_pzt/index.htm

Far-Field Plume Measurements of a Nested-Channel Hall-Effect Thruster

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90664/1/AIAA-2011-1016-314.pd

Discharge Chamber Plasma Structure of a 30 cm NSTAR-type Ion Engine

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76800/1/AIAA-2004-3794-248.pd

Internal plasma potential measurements of a Hall thruster using plasma lens focusing

Magnetic field topology has been found to be a central design concern for high-efficiency Hall thrusters. For future improvements in Hall thruster design, it is necessary to better understand the effects that magnetic field topology has on the internal plasma structure. The Plasmadynamics and Electric Propulsion Laboratory’s High-speed Axial Reciprocating Probe system is used in conjunction with a floating emissive probe to map the internal plasma potential structure of the NASA-173Mv1 Hall thruster [R. R. Hofer, R. S. Jankovsky, and A. D. Gallimore, J. Propul. Power 22, 721 (2006); 22, 732 (2006)]. Measurements are taken at 300 and 500 V500V with a xenon propellant. Electron temperature and electric field are also measured and reported. The acceleration zone and equipotential lines are found to be strongly linked to the magnetic field lines. Moreover, in some cases the ions are accelerated strongly toward the center of the discharge channel. The agreement between magnetic field lines and equipotential lines is best for high-voltage operation. These results have strong implications on the performance and lifetime optimization of Hall thrusters.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87754/2/103504_1.pd

An investigation of internal ion number density and electron temperature profiles in a laboratory-model Hall thruster

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76158/1/AIAA-2000-3422-584.pd

Efficiency Analysis of a Hall Thruster Operating with Krypton and Xenon

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76277/1/AIAA-2005-3683-775.pd

Discharge Chamber Plasma Structure of a 40-cm NEXT-type Ion Engine

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76278/1/AIAA-2005-4250-941.pd