ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

3aPAb1. A nanosecond acoustic source: Experimental investigation of pulsed dielectric breakdown of water and its dependence on pressure and conductivity.

Hugh M. Jones

Dept. of Phys. and Eng. Phys., Stevens Inst. of Technol., Hoboken, NJ 07030

Erich E. Kunhardt

Stevens Inst. of Technol., Hoboken, NJ 07030

Spark gaps are finding use as underwater acoustic sources in sonar and prospecting applications. It is thus important to determine the influence of pressure and conductivity on the dielectric breakdown of water. Well defined rectangular pulses (80-kV, 3-ns rise time, 100-ns duration) have been applied to a gap (0.04--0.21 cm), between Rogowski profile electrodes, containing de-ionized, nondistilled water, de-ionized, distilled water, or sodium chloride solutions (0.001--1.0 M). Breakdown in these liquids has been studied at pressures up to 400 atm. Calibrated voltage dividers situated on the source and load sides of the test gap permitted measurement of the interelectrode potential and the current response. From these measurements, the time lag to breakdown, breakdown voltage, power input to the liquid, and temporal characteristics of the breakdown process have been determined. The breakdown time lag increases with increasing pressure and gap width, and decreases with increasing field. Moreover, it is weakly dependent on the conductivity of the liquid. An Ohmic current-voltage relation has been observed during the prebreakdown stage. A dynamical model has been developed to explain these results and is also presented at this meeting. [Work supported by ONR.]