Optimization of the activity of cavitation generated by pulsed ultrasound

The influence of duration and period of ultrasound pulses on sonoluminescence intensity is studied. Simultaneously with the photomultiplier output the hydrodphone output placed behind the focal spot of a radiator is registered in experiments. It is shown, that the dependencies of cavitation activity on pulse duration and pulse period are of extreme character. With increase of ultrasound intensity the maximum of the sonoluminescence intensity is shifted aside greater pulse periods and smaller pulse durations. The maximal cavitation activity achieved by the variation of the intensity of ultrasound is higher for lower durations and for greater periods of ultrasound pulses. From the results received it is possible to allocate two thresholds of cavitation: the first one corresponds to occurrence of light pulses, and the second one - to step-like increase of the sonoluminescence intensity. The second threshold of cavitation is characterized by the sharp increase of the absorption of ultrasound in a cavitation zone. The reason of this increase is evidently caused by the increase in volumetric bubbles concentration in a cavitation zone.