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Description:
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Ultra -fast gaseous breakdown is an important phenomenon in pulsed power related to ultra wideband systems , plasma limiters , and ultra fast switches . Recent advances in digitizers and pulser technology has allowed for pulses with sub -nanosecond properties to be examined in detail . This thesis examines voltage pulses in quasi homogenous fields with rise times less then 200 ps and pulse widths less then 300 ps . The breakdown is examined in pressures from high vacuum to 600 torr in argon and air . E /N values range from the order of 103 to 106 Td , and are typically above the threshold for the generation of runaway electrons . Also discussed is the design and characterization of a transmission line system including a pulse shaping lens intended to limit wave distortion at a coaxial to biconical geometry . Finite element numerical simulations have been used to explain the behavior of the system .
Diagnostic methods include waveform analysis from fast capacitive voltage dividers , X -Ray detection through a scintillator photomultiplier combination , and optical analysis through fast streak camera imaging . Parameters for the breakdown are established through modeling of the gap . X Ray emissions point to the role of runaway electrons in the breakdown . Electron energy at the anode is roughly determined for various pressure ranges . Streak camera imaging is used to show channel distribution and structure and its dependence on pressure . Results show breakdowns with development times too fast to be explained by standard breakdown mechanics indicating the importance of fast electrons in the event . |