Study on spatial distribution of acoustic cavitation generation using high resolution cavitation sensor

Acoustic cavitation plays a key role in several fields including therapeutic medicine and cleaning. Meanwhile, acoustic cavitation is a hazardous phenomenon due to the damage to targets irradiated by ultrasound such as normal cells in the human body. Therefore, it is important to control cavitation. An accurate technique for measuring the amount of generated cavitation with the aim of its control is required. Therefore, we have been studying a novel accurate cavitation measurement technique that uses the broadband integrated voltage (BIV) calculated from the broadband noise measured by a hollow cylindrical cavitation sensor. In this study, the distribution of BIV in the direction of ultrasound propagation and parallel to the surface of the water in a water vessel was measured using a high resolution cavitation sensor that has improved spatial resolution. The distribution of BIV values measured using the cavitation sensor was compared with the distribution of sonochemiluminescence (SCL) emissions observed from the side of the vessel. In the results, high values of BIV in the direction of ultrasound propagation measured by the cavitation sensor exhibited an interval of approximately 5 mm. This interval corresponds to the half wavelength period of the operating frequency of 150 kHz. The high values of BIV agreed well with the observed distribution of SCL emissions. This indicates that the cavitation sensor has the potential to accurately measure the nodes and antinodes of a standing wave acoustic field. The distribution of BIV values in the direction parallel to the surface of the water also agreed well with SCL. The results show that BIV measured by the cavitation sensor has the potential to become an accurate tool for measuring the spatial distribution of acoustic cavitation generation.