An ultra-high speed laser schlieren technique for studying electrical breakdown in dielectric liquids

A powerful new diagnostic tool employing a Q-switched laser has been developed for the study of very high speed events in dielectrics. In an early experiment, it has been possible for the first time to study in detail cavity formation and growth in n-hexane under uniform field conditions immediately before breakdown. The results show that cavities play a vital initiation role in electrical breakdown, but that they never become very large because of unstable surfaces. This leads to irregular shaped cavities and very high field enhancement in the liquid itself, where impact ionization is likely to occur.