Development of tough anti cavitation hydrophone by deposition of hydrothermally synthesized lead zirconate titanate poly-crystalline film on reverse surface of titanium front layer

Abstract

It is difficult to measure the high intensity ultrasound field with generation of acoustic cavitaion, since the electrode of hydrophone will be damaged by erosion and acoustic cavitation. Therefore, we developed the original miniature hydrophone by using hydrothermally synthesized lead zirconate titanate poly-crystalline film deposited on a reverse surface of a titanium film front layer as protection layer from damage by acoustic cavitation and erosion. Our hydrophone could be used to measure the high intensity ultrasound field with generation of acoustic cavitation such as focal area of 1.6 MHz HIFU treatment equipment and in a vessel of a 47 kHz ultrasound cleaner without any damage. However, we observed the output waveform of the hydrophone without nonlinear distortion in spite of measurement in high intensity ultrasound field like focal area of 1.6 MHz HIFU treatment equipment. We considered on the cause of above problem and its improving methods by computer simulation with MASON's equivalent circuit and one dimensional acoustic transmission model for the titanium front layer. As results, it was found that the cause of above problem was decrease of its receiving sensitivity in higher frequency region. Furthermore, we could propose two types of structure of hydrophones with improved frequency characteristics of receiving sensitivities. One type of hydrophone has titanium front layer thinner than 5μm. Another type has titanium front layer with thickness of 50μm and backing material with specific acoustic impedance of about 24 MRayl.