Committee: 

Dr. Morris Cohen, ECE, Advisor

Dr. Thomas Gaylord, ECE

Dr. Sven Simon, EAS  

Dr. Mitchell Walker, AE

Abstract:

Very Low Frequency (VLF, 3-30kHz) and Low Frequency (LF, 30-300kHz) radio  waves are useful due to their ability to travel around the world in the  Earth-Ionosphere waveguide and excellent skin depth penetration into  conductors. However, generation of these waves is limited due to the fact  that their wavelengths are hundreds of meters to kilometers long. A recently  proposed antenna concept known as VAIPER involves an antenna with  time-varying conductivity. The antenna's properties need to be varied at  nanosecond timescales. This time-varying concept can be realized at low power with COTS components, but high speed switches cannot handle high power. A  plasma is a conducting media with electrical properties that can be varied  rapidly while handling high current flow. Antennas made from plasma have been  constructed and tested in the past, but not with rapidly time-varying conductivity in mind. To determine a plasma's viability as an antenna, its electromagnetic properties must be measured. Conventional plasma analysis techniques do not resolve variations in plasma at the desired speeds. The  objective of the research in this thesis is to develop techniques to analyze a plasma column's electric properties as it is ionized and de-ionized on the nanosecond timescales. Optical techniques are used to determine the time-varying conductivity of rapidly pulsed plasma. The conductivity measurements are used with a basic propagation model to determine whether the experimental plasma columns can support the VAIPER scheme.