High Speed Laser Schlieren Studies of Electrical Breakdown in Liquid Hydrocarbons

The events occurring just prior, during, and after electrical break-down in liquid hydrocarbons have been photographed using 15 ns laser pulses produced with a ruby laser, to illuminate the space between two parallel plate electrodes, and schlieren optics. In this manner it was possible to obtain experimental evidence of the density gradients produced by the movement of charge carriers during prebreakdown and the energy released during and after breakdown. Bysplitting the laser beam and delaying one half by 40 ns with respect to the other, the events occurring in the electrode gap could be studied as a function of time. Attempts to use the light emitted prior to breakdown as trigger signal for the laser were not successful. The initiation and propagation of breakdown are discussed in the light of the available photographic evidence.