Ultraviolet-induced flashover of a plastic insulator using a pulsed excimer laser

Ultraviolet-induced flashover has been observed over stressed, angled, acrylic insulators illuminated by a short (60 ns) pulse of excimer laser light at 249 nm. Flashover has been observed at ultraviolet fluences of 5–65 mJ/cm² for electric field stresses approximately 10–30% of static breakdown stress. Insulators at positive angle (conventional configuration) exhibit a reduced tolerance to ultraviolet light versus insulators at negative angle (unconventional configuration) by approximately a factor of 2, while the presence of impurities at the triple point reduces the tolerance to ultraviolet even further. Flashover is related to the fluence, rather than the power density, for short pulses, and the production of photoelectrons is a likely mechanism for the initiation of flashover.