Dynamic behaviour of laser nucleated bubbles in a focused ultrasound field

A reference facility to control the cavitation of single bubbles and bubble clouds, using optical and acoustic fields, has been designed and developed at the National Physical Laboratory, UK. The facility consists of a cuboid acoustic chamber, with optical windows on four sides and four transducers mounted on a truncated tetrahedron cap, a Q-switched laser, and an optical beam splitting system able to form either single or multiple beams. This work presents a characterization of this facility: the acoustic pressure field inside the acoustic chamber was measured with a combination of laser refractometry and hydrophone scans, to determine the locations where cavitation can be studied, while the optical threshold was quantified by observing nucleation as a function of the beam parameters. This work also presents some preliminary acoustic emission data and high-speed observations of bubble dynamics.