Sonoluminescence from transient cavitation at high pressures in water and acetone

Abstract

In highly degassed, clean liquids, transient acoustic cavitation can be triggered by fast neutrons, a phenomenon that has been known since ∼1960’s. The kinetic energy acquired by the nuclei allows it to ionize a small volume (∼100 nm dia.) in the liquid, creating a vapor cavity that would normally last a couple of microseconds. If the acoustic amplitude and phase are right, this cavity expands by several orders of magnitude (∼500 to 1500 microns dia.) and then collapses, emitting a short flash of light (1 to 40 nsec). The bubble continues to expand and collapse for several hundred cycles, eventually evolving into a larger (2 to 6 mm dia.) bubble cloud which lasts several milliseconds, depending on the conditions. The time duration of the light pulses is longer and their amplitude larger than those of single bubble sonoluminescense in water (∼100 to 300 psec, 105 photons/flash). The amplitude and time evolution of the light flashes has been analyzed as a function of the driving conditions and compared with computer simulations in an effort to infer the maximum plasma temperatures and densities, and perhaps the presence of shock waves, in the cavities.