Breakdown of water under long term stress

If high-dielectric-constant fluids like water could be made to support electric stress for times approaching a millisecond, it should be possible to charge megajoule pulsed-power systems directly from rapidly discharging mechanical devices. The limit on allowable stress times comes from the relatively low resistivity of high-dielectric-constant fluids. Resistivity may be increased by improving the purity of the fluid and by cooling it. This paper reports on the breakdown strength of water purified to its intrinsic resistivity level, then chilled nearly to freezing. Pulses of several hundred microseconds duration were applied to electrode areas of 80, 400, 2000, and 10,000 cm/sup 2/. Small samples showed a hysteresis effect where the strength of the sample depended strongly on previous pulses. A typical lowering of the dielectric strength with increased area (area effect) was also observed. These data are used to demonstrate the applicability of the statistical model of area effects.