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Nanosecond-pulse breakdown indicates special characteristics depending on the pulse rise-time and duration. Based on a repetitive nanosecond-pulse generator, breakdown phenomena of parallel-plane gaps in nitrogen were investigated with single pulse and repetitive bursts under different gap conditions. The relationships between applied voltage, pulse repetition frequency, breakdown time lag, repetitive pulse stress time and the number of applied pulses are presented. The curves regarding E-field strength, breakdown time lag and gas pressure are also obtained. The experimental results show that breakdown characteristics with repetitive nanosecond-pulses are different from that with single pulse. Repetitive nanosecond-pulse breakdown is concerned with the accumulation effect that is attributed to residual ions and metastable species survived from previous pulses. in addition, a modified empirical formula about E-field strength, breakdown time lag and gas density is given for the breakdown data. [ABSTRACT FROM AUTHOR]

Based on a Marx generator and a coaxial pulse forming line, an experimental investigation of surface flashover characteristics in vacuum is conducted by using nanosecond pulses of 10 ns rise time and 30 us full width at half maximum (FWHM). Insulator dielectrics chosen for this investigation are Teflon, PMMA and Nylon. The tested factors include gas pressure, cone angle of conical frustum, diameter and length of cylindrical insulator, material and shape of electrode, and contact style between insulator and electrodes. The effects of these parameters on the surface flashover characteristics are described and analyzed in this paper. In addition, the character of flashover time lag in the nanosecond range, and surface flashover theory in vacuum charged by nanosecond pulses are also discussed. [ABSTRACT FROM AUTHOR]

This paper illustrates images of dielectric-barrier discharge (DBD) excitated by repetitive unipolar nanosecond pulses in atmospheric air. Different images are obtained for three barrier dielectrics and various gap lengths. Discharge images show that the nanosecond-pulse DBD observed with the eye is a diffuse glowlike mode when air gap is 2 mm; clear filamentary discharge is seen with the eye in the case of air gap of 8 mm. The results show that gap length and dielectrics are the important factors influencing the transition from diffusive to filamentary discharges. [ABSTRACT FROM AUTHOR]