Masters Theses

Abstract

"First, a globally-averaged RF plasma model is used to investigate exit conditions immediately following a RF pre-ionization stage. Analysis shows that reducing pulse duration from 10⁻⁶ to 10⁻⁷ seconds increases peak ion energy fraction by 17% (from 16 to 33%) and doubles final conductivity. Pulse waveforms are square in nature, and ion energy fraction is defined in this work as the percentage of total input energy entrained in ions. Increasing total energy deposition from 5 to 160 mJ increases ion energy fraction from 33% to 58% at a 200 ns pulse duration. This increase is not linear however, showing instead a diminishing return with a peak fraction plateau estimated at 65% to 70%. A constant (time-average) power analysis reveals that, across all power levels (10 to 100 kW), energies (5 mJ to 1 joule), and durations (0.05 to 10 µs), peak ion energy fraction consistently occurs approximately 1 to 2 µs before peak conductivity.

Second, single particle and particle-in-cell simulations are used to elucidate breakdown physics in a ringing theta-pinch with bias magnetic field. The analyses presented here agree with previously conducted experimental results showing that gas breakdown occurs only upon approximate nullification of the bias magnetic field by the pulsed theta-pinch magnetic field. Parametric analysis of the peak electron energy as a function of the bias and pre-ionization magnetic fields reveals that; 1.) when bias magnetic field is [double tilde] 97% of the pre-ionization magnetic field the peak electron energy is highly erratic, and 2.) high electron energy levels require a pre-ionization to bias magnetic field ratio of 2 to 1 or higher"--Abstract, page iii.

Advisor(s)

Rovey, Joshua L.

Committee Member(s)

Isaac, Kakkattukuzhy M.
Castano Giraldo, Carlos Henry

Department(s)

Mechanical and Aerospace Engineering

Degree Name

M.S. in Aerospace Engineering

Sponsor(s)

United States. Air Force. Office of Scientific Research

Publisher

Missouri University of Science and Technology

Publication Date

Fall 2012

Pagination

x, 79 pages

Note about bibliography

Includes bibliographical references (pages 74-78).

Rights

© 2012 Warner Charles Meeks, All rights reserved.

Document Type

Thesis - Open Access

File Type

text

Language

English

Subject Headings

Radio frequency integrated circuitsPlasma acceleratorsSpace vehicles -- Electric propulsion systems -- Testing

Thesis Number

T 10124

Print OCLC #

852160303

Electronic OCLC #

908859396

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