Electrostrictive Cavitation under Nanosecond Pulsed Electric Field

Plasma discharge in water under nanosecond pulsed electric field has received extensive research attention in the last decade. Previous work has demonstrated that the physical mechanism of the breadkown initiation is cavitation due to electrostriction in strong imhomogeneous fields. The first electrons are released into the cavities and then undergo multiplication, eventually leading to the initial plasma discharge channel. However, the unknown characterisctics of the cavitation zone, e.g., cavity size and density, prohibit a clear delineation of the electron processes at the initial stage of the nanosecond breakdown. This work aims to explore the electrostrictive cavitation dynamics to extract key features of the cavitation zone which sets stage for the electron processes. In the literature, most of the discussions of cavitation have been focused on the kinetics following the Zeldovich-Fisher model. In this work, we extend the kinetic model to a dynamic one by including (a) the cavity growth after formation, i.e., the Rayleigh bubble equation; and (b) the "feedback" to the negative pressure due to cavity formation and growth. The preliminary numerical calculations indicate that this dynamic model results in the saturation of cavitation and a spectrum of cavity sizes. The results of this work will be used in the subsequent work to test alternative models to clarify the electron processes.