Homogeneous Nucleation of 4He Crystals by Acoustic Waves

We have recently found experimental evidence for the homogeneous nucleation of crystals in metastable liquid 4He at high pressure. For this we combined the focusing of a high intensity spherical acoustic wave with a simple light scattering technique. We discuss the analysis used to distinguish between nucleation of bubbles in the negative pressure swings of the wave from nucleation of crystals in the positive swings. We also discuss the interest of our results and future developments of our experiment in the general context of the study of nucleation and instability limits in phase diagrams.