Use of Second Sound to Investigate the Inhomogeneous Density Distribution of the Superfluid Part of Helium II Near tne λ Point
Ginzburg V. L., Sobyanin A. A.
One can hope to investigate the density distribution of the superfluid part of helium II near the λ point by "sounding" the helium (in particular, the boundary between helium I and helium II in a gravitational or electric field) by means of second-sound waves.