Visual Observation of a Sound-Induced Bubble in Liquid 3He–4He Mixtures

Abstract

We report visual observation of a sound-induced bubble in superfluid 3He–4He liquid mixtures using a high-speed camera at a rate of 1 msec/frame. The experiments were performed in the 3He dilute phase of phase-separated mixtures at 300 mK. The resonant frequency of the piezoelectric transducer was 9.36 MHz and the diameter of the active electrode was about 4 mm. When an acoustic wave pulse of sufficient magnitude was applied to the dilute phase from the transducer under saturated vapor pressure, a single bubble was nucleated on the active area. The bubble expanded almost spherically on the transducer, as it reached maximum size, it started shrinking, detached from the transducer, and collapsed. We also investigated the motion of the bubble in mixtures with a 3He concentration of 25% at 750 mK. In this case, the bubble grew elliptically on the transducer and detached from it without much change in shape.