Prebreakdown Phenomena Observations

Since 1933, prebreakdown phenomena in liquids mainly have been investigated physically. With the development of observation instruments and techniques such as ultra-high-speed camera, nanosecond square-pulse-generator, optoelectronics, laser Schlieren, laser doppler, etc., the transition mechanism from the intrinsic electrical breakdown to the cavitational breakdown has been quantitatively investigated in cryogenic and hydrocarbon liquids both electrically and optically. From the optically observed results, it is suggested that even if the time lag of the final breakdown is less than 50 ns, the cavitational breakdown mechanism had to be taken into consideration. This is confirmed by the fact that the electron energy obtained from the applied field at the prebreakdown state was two times larger than the C-H bonding energy of hydrocarbon liquids.