Nucleating bubble clouds with a pair of laser-induced shocks and bubbles

Abstract

AbstractLaser-induced optical breakdown at two spatial locations in ultrapure water saturated with ambient gas is used to nucleate microscopic bubble clouds with lifetimes of tens of nanoseconds. The liquid is ruptured via the interaction of a pair of laser-induced shocks and bubbles. We find that the acoustically nucleated micro-bubbles appear in a localized region defined by the plane that bisects the pair of foci, where rarefaction waves (reflected from the laser-induced bubbles) merge. We measure the probability for acoustic nucleation as a function of the separation between the foci, and the minimum pressures for each separation are calculated with Euler flow simulations. The simulations show that the liquid is exposed to negative pressures for 3–17 ns. A statistical threshold pressure for cavitation inception (0.5 probability) of $- 20. 1\pm 3. 4~\mathrm{MPa} $ is extracted from the measured probabilities and the calculated minimum pressures.