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The physics of high-velocity ions in the Hall thruster near-field

Citation

Sullivan, Regina M. (2010) The physics of high-velocity ions in the Hall thruster near-field. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:04022010-134100215

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Abstract

A study of the physics underlying high velocity ion trajectories within the near-field region of a Hall thruster plume is presented. In this context, "high velocity" ions are ions that have been accelerated through the full potential drop of the thruster (sometimes referred to as "primary energy" or "primary beam energy" ions). Results from an experimental survey of an SPT-70 thruster plume are shown, along with simulated data from a Hall thruster code and from a plasma sheath model. Two main features are examined: the central jet along the Hall thruster centerline, and the population of high velocity ions at high angles.

In the experimental portion of the investigation, three diagnostic instruments were employed: (1) a Faraday probe for measuring ion current density, (2) an ExB velocity filter for mapping ions with the primary beam energy, and (3) a Retarding Potential Analyzer (RPA) for determining ion energy distributions. In the numerical portion, two codes were employed: (1) a hybrid-PIC Hall thruster code known as HPHall, and (2) a model of the plasma sheath near the exit plane of the thruster, which was developed by the author.

A comparison between the measured and simulated data sets is made, to analyze the degree to which different mechanisms are responsible for the evolution of the thruster plume in the near-field region. This analysis shows that the central jet is both a function of symmetric expansion of the ion beam as well as asymmetry in the internal potential field of the thruster. Additionally, it is suggested that high energy, high angle ions could be generated given a specific internal electric field configuration, while oscillations are ruled out as the cause of these ions. The results from the sheath model show that while the sheath can change trajectory angles by 10 to 20 degrees, it can not fully explain the presence of high angle ions with high energies.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Electric propulsion, Hall thruster plumes, near-field plume, plasma sheath physics, hybrid-PIC simulation, central jet physics, high angle high velocity ions
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Aeronautics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Shepherd, Joseph E. (advisor)
  • Johnson, Lee K. (co-advisor)
Thesis Committee:
  • Pullin, Dale Ian
  • Bellan, Paul Murray
  • Shepherd, Joseph E. (chair)
  • Johnson, Lee K.
Defense Date:3 March 2010
Record Number:CaltechTHESIS:04022010-134100215
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:04022010-134100215
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:5695
Collection:CaltechTHESIS
Deposited By: Regina Sullivan
Deposited On:19 Apr 2010 15:22
Last Modified:07 Feb 2014 18:36

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