Microwave diagnostics on a railgun plasma
Grant, Gregory T.
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This thesis describes microwave interferometry measurements on the High Energy Railgun Apparatus (HERA) at Texas Tech University. Chapter I discusses railguns in general, basic railgun theory, and problems encountered whh railguns. The physical railgun system is described and illustrated as well as the timing and firing system, and the data acquishion system. Chapter II contains a general discussion of interferometry, a detailed discussion of the microwave interferometer used on the HERA railgun, and a discussion and analysis of the expected signal from the detector of the HERA interferometer. Chapter III discusses the acquishon of the experimental data. It describes how the interferometer was "zeroed" before each shot and shows how attenuation and reflection of the interferometer microwave probing beam played a role in the collection of the data. This chapter also describes techniques which could be used to cut down on microwave reflections at dielectric interfaces on the railgun bore. Chapter IV is a detailed analysis of the shot data. This analysis includes a figure for each shot of interest and a table to describe the shot condhions. It also provides calculations and observations based upon the observed waveforms. These calculations are shown for the HERA railgun first whh a 1.8 cm square bore, and then with a 1 cm round bore. Chapter IV also gives resuhs and conclusions of this research. Trends in the data are pointed out and speculations about the significance of these trends are given. Conclusions are drawn and final remarks and recommendations are made.