Abstract
A dense fog consisting of superfluid 4He droplets can be generated in helium vapor up to a height of 4–6 cm from the helium surface by driving a piezo transducer plate immersed under the liquid. The average droplet size ranges from about 100 μm at a drive frequency of 1 kHz to 10 μm at 100 kHz, and the frequency dependence is consistent with the capillary-wave dispersion relation of the helium surface, with the droplets ejected from the surface being about one wavelength in diameter. It appears that the helium vapor is set into motion along with the droplets, greatly reducing the viscous drag on the droplets and making possible the substantial fog heights above the surface.