Impulse breakdown in PMMA under megavolt, nanosecond excitation

Abstract

Factors that affect the breakdown strength of a solid dielectric include the electrode geometry, specimen thickness, specimen homogeneity, and the nature of the applied electrical excitation. In some applications, thick solid dielectrics are subjected to extremely high fields for periods of nanoseconds. The integrity of such systems cannot be extrapolated from the behavior of thinner dielectrics or from dielectrics subjected to longer pulses. Moreover, experiments on thick specimens in the nanosecond time regime have a particular interest because they can yield information on the mechanism of breakdown. The goal of the present work is to obtain this information on the mechanism of breakdown in solids. Single impulse excitation is employed, each impulse having an amplitude in the mega-volt range, large enough to highly overvolt relatively thick specimens while using a uniform field geometry. The damage morphology is examined.