Investigation of the Thickness and Critical Velocity of a Moving Unsaturated Superfluid Film Using Doppler Shifted Third Sound.
CALIFORNIA UNIV LOS ANGELES DEPT OF PHYSICS
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The velocity of third sound waves on a moving unsaturated superfluid film has been measured by the time of flight technique. The thickness of the moving film was probed by the average of the two Doppler shifted velocities. To within experimental precision, no changes in film thickness were observed as the film velocity was increased. Several possible resolutions to this paradox are presented. The maximum observed Doppler shift measured the critical flow velocity. Modified author abstract