Abstract
By forcing He II out of a tube, large-scale vortex rings with diameters of about 1 cm and normal-fluid and superfluid circulations of some cm 2/s were produced. The circulations, the vorticity distributions, the dimensions, and also the translational velocity of these vortex rings were investigated by means of a method of measurement based on the Doppler effect of first and second sound. All parameters of the vortex rings turned out to be independent of temperature. Already during the ejection of the fluid both the normal and the superfluid circulation were identical. This result is explained in terms of the formation of a superfluid boundary layer at the inner wall of the tube and the interaction of normal and superfluid flow due to the mutual friction force.
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