Electrical and optical characteristics of water under high electric stress

In order to determine the electrical characteristics of water under high electric stress, we have measured the current-electric field (I-E) characteristics of distilled water with a resistivity of 200 k/spl Omega/cm, up to electric field intensities of 1 MV/cm. The gap between a 1.7 mm diameter sphere and a plane stainless steel electrodes was varied between 50 /spl mu/m to 400 /spl mu/m. Voltage pulses with duration of 200 ns and amplitude of up to 40 kV, provided by a 50 /spl Omega/ Blumlein generator, were applied to the electrodes. In addition, measurements of changes in the index of refraction of distilled water under high electric stress were performed, using laser Schlieren method and Mach-Zehnder interferometry with a temporal resolution of one nanosecond. With the electric fields in excess of 500 kV/cm the increase in the current was found to be super linear. This is in accordance with the general I-E characteristics for polar liquids. Optical measurements at average electric fields of up to 1 MV/cm revealed that a layer with decreased index of refraction emerges from the surface of the spherical electrode, which serves as anode. Shifting of the fringes is observed even after the voltage pulse ends. This might be an indication of change in composition of water after voltage applications.