thesis

Calibration and application of a B-dot sensor to study the initiation of vacuum surface flashover

Abstract

\u27Calibration\u27, as the name suggests is the act of checking or adjusting the accuracy of a measuring instrument by comparison with a standard. Two techniques, the equal length test and the short circuit test, have been developed to determine the characteristic impedance and propagation coefficient of a single lossy transmission line and a lossy transmission line network in cascade based solely on the input reflection coefficient S-parameter, S11, VNA measurements over a wide bandwidth of frequencies. For the transmission line network case, the characteristic impedance and propagation coefficient for each line in the cascade, excluding the last line, are known. Theoretical expressions needed for interpreting VNA measured data have been developed. A wideband, coaxial cable calibration test stand is characterized based on the novel equal length technique. The test stand is used to calibrate a B-dot in the frequency domain to obtain its response function. To verify the calibration process, the calibrated B-dot will be used to measure the surface current density on a radial transmission driven by a pulsed power source. These results will be compared against simulation using a Graphical Large Scale Plasma (GLSP) code. This calibrated B-dot will be used in future surface breakdown pulse power experiments on plastics measuring fast sub-nanosecond rise time phenomena

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