PZFlex A Robust Hydrophone for HIFU Metrology

Abstract. The high acoustic intensities generated by HIFU systems cause conventional
hydrophones to fail before measurements can be reliably made. To address this challenge, we
present a new piezoelectric needle hydrophone, which is resistant to cavitation while possessing
a flat frequency response (+/- 3 dB from 1 to 10 MHz) and a small effective aperture (400
micron effective diameter). This hydrophone has been used in a high intensity field (1.5 MHz
tone burst of 30 microseconds and 3% duty cycle, with rarefactional pressures exceeding 4 MPa
and positive pressures exceeding 15 MPa) without degradation in the hydrophone's performance,
as indicated in before-and after calibration checks of the device.
Keywords: Hydrophone, HIFU, cavitation