The underwater spark; A photographic light source of high intrinsic brilliance

WHEN an impulse voltage of sufficient magnitude is applied to underwater electrodes, a gaseous conduction channel forms across the gap. If the rate of current rise is thousands of amperes per microsecond, the growth of the gaseous channel is greatly restrained by the inertia of the water and this results in unusually high gas pressure, current density, and temperature. The rapid vaporization of the water at the channel boundary also contributes to the high gas pressure.