Dielectric Breakdown and Time Lags in NaCl Crystals under Ultraviolet Irradiation

The electric strengths and time lags to breakdown in NaC1 single crystals have been measured using flat-topped impulse voltages with and without ultraviolet irradiation. The results show that radiation reduces the mean electric strength of annealed, unannealed, and plastically deformed specimens, but has no significant effect on the mean statistical time lag. Plastic deformation increases and annealing decreases both the electric strength and time lag. An increase in specimen thickness or an increase in overvoltage also causes a decrease in the mean statistical time lag. All observed phenomena can be explained by a lti-multielectron-avalanche mechanism.