Thresholds for eavitation produced in water by pulsed ultrasound

Abstract

Initial results of an experimental investigation of transient cavitation produced by pulsed ultrasound are presented. Water is irradiated with a focused transducer and the subsequent cavitation detected acoustically by a second transducer. The detection technique relies upon the scattering of the irradiation field by the bubble cloud associated with the transient cavitation. A novel feature of the experimental apparatus is a system with which potential cavitation nuclei can be passed directly through the focal region of the irradiation transducer. The threshold for transient cavitation was measured for 1‐ and 2.25‐MHz pulses having durations from a few cycles to 500 μs and repetition frequencies from 50 to 5000 Hz. The data are consistent with, but extend, those of Crum and Fowlkes [Nature 319, 52–54 (1986)] in which sonoluminescence emission was used as the cavitation criterion. The results of the experiment are discussed with regards to the predictions of present theories, in particular, that of Apfel [IEEE UFFC 33, No. 2, 139–142 (1986)]. [Work supported by NIH. AAA acknowledges the support of the F. V. Hunt Postdoctoral Fellowship.]