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Hybrid-PIC modeling and electrostatic probe survey of Hall thrusters

IP.com Disclosure Number: IPCOM000128068D
Original Publication Date: 1998-Dec-31
Included in the Prior Art Database: 2005-Sep-14
Document File: 13 page(s) / 33K

Publishing Venue

Software Patent Institute

Related People

Fife, John Michael: AUTHOR [+3]

Related Documents

http://theses.mit.edu:80/Dienst/UI/2.0/Describe/0018.mit.theses/1998-238: URL

Abstract

In order to study the physics of the acceleration process in Hall thrusters, an evolved hybrid particle-in-cell (PIC) numerical model was developed. A set of quasi-one-dimensional fluid equations are used for electrons, and a particle-tracking Boltzmann solver is used for the heavy species. The two solutions are linked by charge neutrality. A novel statistical approach to particle creation and tracking is employed which reduces computational time. To provide boundary conditions for the numerical model, and to verify its accuracy, an extensive set of electrostatic probe measurements were performed in the plume of an SPT70. Various probe geometries were used, including triple probes, to measure the timeaveraged plasma parameters in the near-plume. Also, AC components of discharge current and floating potential were measured. The combined experimental and numerical results are used to examine phenomena such as the nature of low-frequency discharge oscillations, the interaction of the thruster walls with the plasma, the distribution of ion energies ejected from the thruster, and the effect on efficiency of facility background pressure. Performance results from the numerical model agree well with measurements. A formula for the change in measured efficiency versus facility pressure is also presented, based on numerical results. Widening of the ion distribution of energies is seen, and attributed to time variation of the electric field, due to oscillations. Measured low-frequency oscillations seem to be related to an ionization instability observed in the numerical model, but conclusive evidence is not found. Although the model predicts strong electric fields outside the acceleration channel, experiments do not. The discrepancy is believed to be due to localized anomalous electron conductivity caused by azimuthal asymmetry. Thesis Supervisor: Manuel Martinez-Sanchez Title: Professor

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 This record is the front matter from a document that appears on a server at MIT and is used through permission from MIT. See http://theses.mit.edu:80/Dienst/UI/2.0/Describe/0018.mit.theses/1998-238 for copyright details and for the full document in image form.

Hybrid-PIC Modeling and Electrostatic Probe Survey of Hall Thrusters

by

John Michael Fife
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Aeronautics and Astronautics

at the Massachusetts Institute of Technology

September 1998 [February, 1999]
SIGNATURE OF author: [[signature omitted]]

Department of Aeronautics and Astronautics

September 30, 1998

CERTIFIED BY: [[SIGNATURE OMITTED]]

Manuel Martinez-Sanchez

Professor Thesis Supervisor

Kenneth S. Breuer
Principal Research Scientist
Ian H. Hutchinson
Professor
John J. Deyst
Professor
ACCEPTED BY: [[SIGNATURE OMITTED]]

Jaime Peraire

Chairman, Department Graduate Committee ARCHIVES MASSACHUSETTS INSTITUTE OF TECHNOLOGY LIBRARIES MAY 17 1999

Massachusetts Institute of Technology Page 1 Dec 31, 1998

Page 2 of 13

Hybrid-PIC modeling and electrostatic probe survey of Hall thrusters

Hybrid-PIC Modeling and Electrostatic Probe Survey of Hall Thrusters by John Michael Fife

Submitted to the Department of Aeronautics and Astronautics on September 30, 1998, in partial fulfillment of the requirements for the degree of Doctor of Philospohy in Aeronautics and Astronautics

Abstract

In order to study the physics of the acceleration process in Hall thrusters, an evolved hybrid particle-in-cell (PIC) numerical model was developed. A set of quasi-one-dimensional fluid equations are used for electrons, and a particle-tracking Boltzmann solver is used for the heavy species. The two solutions are linked by charge neutrality. A novel statistical approach to particle creation and tracking is employed which reduces computational time. To provide boundary conditions for the numerical model, and to verify its accuracy, an extensive set of electrostatic probe measurements were performed in the plume of an SPT70. Various probe geometries were used, including triple probes, to measure the timeaveraged plasma parameters in the near-plume. Also, AC components of discharge current and floating potential were measured. The combined experimental and numerical results are used to examine phenomena such as the nature of low-frequency discharge oscillations, the interaction of the thruster walls with the plasma, the distribution of ion energies ejected from the thruster, and the effect on efficiency of facility background pressure. Performance results from the numerical model agree well with measurements. A formula for the change in measured efficiency versus facility pressure is also presented, based on numerical results. Widening of the ion distribution of energies is seen, and attributed to time variation of the electric field, due to oscillations. Measured low-frequency oscillations seem to be related to an ionizati...