Sub-Critical Flow in the Helium II Film

Abstract

While in most observations on the helium II film, transport at the critical velocity has been studied, the present paper describes observations of film transfer at velocities less than the critical. Three different methods of investigation have been employed. The first is an analogue of an electrical circuit embodying a current-potential measurement on a superconductor. The second method uses as indicator the formation of bulk liquid out of a film which passes over a surface of varying perimeter. In these two methods film transfer occurs from a higher to a lower meniscus of bulk liquid. In the third method film transfer is initiated by the introduction of a thermal gradient and transfer rates under varying heat input are studied. The experiments show conclusively that, similar to the phenomenon of superconductivity, below a critical velocity, flow of helium through the film is completely free of dissipation. The third method has been used to determine the heat of transport for the film, and these experiments are described and discussed in an Appendix.