Possible vortex production by a vibrating wire in superfluid He-3-B

We observe spectacular features on the force-velocity characteristic of a v ibrating wire resonator in superfluid He-3-B at ultralow temperatures. Ther e are both plateaux and discontinuities in the characteristic. The plateaux seem to have two separate critical velocities where firstly some 'event' o ccurs, which causes the wire to lose energy and slow down, followed by a se cond critical velocity where the 'event' decouples. The shape of the pulses so created depends on the precise position on the particular plateau. At t he low-velocity end of the plateau, the pulses show a sudden decrease in ve locity followed by a gradual growth, whereas at the high-velocity end the p ulses consist of a sudden increase in velocity followed by a gradual decrea se. Eventually, the pulsing ceases indicating a saturation effect. We specu late that these events are due to vortex creation and annihilation,separati on. (C) 2000 Elsevier Science B.V. All rights reserved.