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Subnanosecond Breakdown of Insulating Media
Final rept., 1 Jul 2003-31 Aug 2006
TEXAS TECH UNIV LUBBOCK DEPT OF ELECTRICAL ENGINEERING
Pagination or Media Count:
Breakdown in argon and air at pressures below one atmosphere, for quasi homogeneous electric fields with amplitudes of up to 3 MVcm, risetimes 250 ps, and gap distances on the order of millimeters, is investigated. The setup consists of a RADAN 303 A pulser and pulse slicer SN 4, an impedance-matched oil-filled coaxial line with a lens-transition to a biconical line in vacuum or gas, and an axial or radial gap, with a symmetrical coax arrangement on the other side of the gap. Capacitive voltage dividers allow to determine voltage across as well as conduction current through the gap, with a sampling rate of 50 ps and an analog bandwidth of 6 GHz. Auxiliary diagnostics include x-ray absorber foil spectroscopy, and streak camera imaging. Breakdown is governed by runaway electrons, with multi-channel formation and high ionization and light emission in a thin cathode layer only. In argon and air, time constants for the discharge development have a minimum of around 100 ps at several 10 torr. A qualitative understanding of the observed phenomena and their dependence on gas pressure is based on explosive field emission and gaseous ionization for electron runaway conditions.
APPROVED FOR PUBLIC RELEASE