Nucleation by Cosmic Rays in Ultrasonic Cavitation

Abstract

Nucleation in ultrasonic cavitation is due to cosmic rays. The neutron component seems sufficient to explain the experiment in water, through the creation of oxygen recoil nuclei which would act as nucleating agents; energy deposit and radiolytic effects produce small overheated and oversaturated regions in which cavities of radius larger than the critical one may originate. The microcavities would be created in the absence of a sound field and grow to visible size when an adequate sound field is applied. Enclosing the tank in which the liquid is contained with lead or paraffin screens results in threshold variations which are due to absorption and slowing down of primary neutrons and, probably, to nuclear reactions induced by the gamma and meson components of cosmic radiation in the screen material through the production of secondary neutrons.