Persistent currents in saturated He II films detected through film flow measurements: Addendum to ?Does a persistent current exist in a superfluid helium film??

Abstract

The existence of a persistent current in a saturated He ll film which is adsorbed on the walls of a container of typical dimensions 1 cm is demonstrated. The persistent current is produced by rotation and detected by measuring the critical film flow rate.The conditions for the successful excitation of persistent currents in saturated helium films are still unexplored. In one case t'z persistent currents in saturated helium films have been successfully generated inside closed annuli made of metal or glass capillaries. In these experiments persistent currents are detected via the kinetic energy of the mass flow, which excites level oscillations in partly filled containers connected to the loop. No persistent currents have been observed in cylindrical containers of typical dimension 1 cm. 3"4 Here the cylinder, whose walls were covered by the film, was rotated in an attempt to produce a superfluid mass flow. The detection of persistent currents was by measuring either the critical film flow rate as a function of the container wall velocity 3 or the Doppler shift of the third sound velocity. 4In this paper we describe experiments in which we have observed persistent currents in saturated films adsorbed on the walls of a comparatively large cylindrical container. The presence of a persistent current was demonstrated by measuring the critical film flow rate R c. Film flow could be thermally induced in a cylindrical container parallel to the axis about which it could *"Does a Persistent