Imbibition of Liquid Helium in Aerogels
Résumé
We report optical measurements of the imbibition of liquid helium in a sample of silica aerogel with 90 % porosity. Both direct imaging and light scattering experiments were performed to determine the dynamics and the properties of the liquid-gas interface in both the normal and superfluid phases of liquid helium. In the normal phase, a classical Lucas Washburn behavior is observed for the rise of the imbibition front while the behavior in the superfluid phase is markedly different, as the fluid invades the sample from all sides with a constant speed. In both phases, the interface is rough, leading to light scattering. In addition, condensation ahead of the imbibition front is observed at low temperature in the superfluid phase.