ASA 124th Meeting New Orleans 1992 October

3aPA10. On the fundamental physical mechanisms leading to electrical breakdown in spark transducers.

Stephen P. Sutton

Allen H. Olson

Naval Command Control and Ocean Surveillance Ctr., RDT&E Div., Code 711, 271 Catalina Blvd., San Diego, CA 92152-5000

It is widely assumed that a liquid state leader mechanism leads to arc formation in spark discharge sources, although this hypothesis has failed to yield models sufficient for transducer design. Experimental results are presented that support a new model. Electrical breakdown between spherical electrodes immersed in seawater is shown to be highly correlated with dissipation of a threshold amount of energy to joule heating in the fluid. Acoustic measurements demonstrate that this threshold corresponds to the energy required to initiate vaporization. It is further shown that breakdown times are linearly correlated to the time at which the vaporization threshold is reached. These results are interpreted as strongly supportive of a new model based on vapor formation and subsequent ionization leading to arc formation.