HIGH-VOLTAGE SUBNANOSECOND BREAKDOWN

Present-day ultra-wideband radiation sources produce Megavolt pulses a t hundreds of picosecond (ps) risetimes, Empirical data on the breakdo wn characteristics for dielectric media at these short time lengths an d high voltages are either extremely limited or nonexistent. In suppor t of the design of these ultra-wideband sources, we are investigating the breakdown characteristics, at these voltages and time lengths, of several liquids and high-pressure gases. These include air, N-2, H-2, SF6, and transformer oil. Gap voltages attained were over 700 kV and g as pressures were over 150 atm (15 MPa), Breakdown times achieved were on the order of 600 ps. Electric field strengths observed for given b reakdown times were higher than predicted by other investigators. An e mpirical fit is presented for the data obtained.