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Numerical Modeling of Ion Dynamics in a Carbon Nanotube Field-Ionized Thruster
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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Carbon nanotube field ionization technology has the potential to make ion propulsion feasible for use in micro- and nano-satellites. To better understand the phenomenon and optimize the ion thruster design, it is useful to have an accurate model of the system. Numerical modeling of large-scale electron bombardment ion engines is a relatively mature field, but modeling of field-ionized ion engines is in its infancy. A simpler code may be appropriate for the early modeling stages of carbon nanotube field ionization technology one such software package is spiffe. Spiffe is intended for modeling axisymmetric radio frequency guns, but it contains all the code necessary for basic modeling of ion optics in a field-ionized ion thruster. This work analyzes the feasibility of spiffe software for use in modeling field-ionized ion thrusters. It also provides detailed procedures for its use. In this work, spiffe is first verified to agree with theoretical predictions of limits in a one-dimensional approximation using electrons. Two primary geometries and their boundary conditions are investigated. The geometry is then varied to test the limits of the one-dimensional approximation. This was further altered to simulate singly-charged Argon ions and verified against theoretical onedimensional limits. A supplemental users guide was developed to aid students with minimal programming experience to quickly become familiar with the methods used in spiffe and the impact of program options on the results. A guide to quickly post-processing the data was also developed.
APPROVED FOR PUBLIC RELEASE