Study into the Dynamics of the HIFU Cavitation Zone Development

It has been studied the dynamics of the cavitation zone development. Cavitation zone was generated by high intensity focused ultrasound (HIFU) in pulsed mode. Three stages of the process were identified. Sonoluminescence (SL) is absent at the first stage. The output signal of the hydrophone which is placed above the focal point of the transducer, is constant if the voltage applied to the transducer is constant. It is increased linearly if the ultrasound intensity is increased linearly. The sonoluminescence is appeared at the second stage. Its intensity is increased slowly at this stage. At the third stage a jump-like increase of SL is observed. The acoustic transparency of the cavitation zone is decreased simultaneously. Cavitation noise spectra are changed significantly with stages of that cavitation zone development. This is indicative that the different regimes of sonication could be identified by spectral analysis of cavitation noise.