Optical studies of prebreakdown cathode processes in deionized water

The initial stage of prebreakdown cathode processes was studied with the help of Schlieren method and electrooptical Kerr effect, with laser light exposure of ap 3 nanosecond. Experiments were performed by using triangular voltage pulses with time rise of ap 1 mus, time decay of ap 0.1 mus and total width of ap 2 mus. Interelectrode gap was 3 - 5 mm with electrode diameter of 50 mm. Field intensity varied from 300 kV/cm up to 500 kV/cm. Initial singular optical heterogeneities with size of 10-10²mum were registered at E ges 380 kV/cm. Density spherical disturbances with epicenter positioning over cathode are registered when cathode ldquoclusterrdquo reaches the size of ges 10^-2 cm. Amplification of electric field that exceeds several times the average field in the gap is registered near the cluster. However, fast discharge was generated from anode. Experiments performed with unrestricted voltage pulse duration at . ap 300 kV/cm established that within 6 - 8 mus cathode disturbances increased up to the size of 2 - 4 mm that initiates the breakdown.