Quantum Vortex Events in the Critical Flow of Superfluid Helium-4 Through Microscopic Apertures

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9403522 Zimmermann This is a research effort in the area of low temperature condensed matter physics. The project will investigate critical velocities and phase-slip in the flow of superfluid helium-4 through submicron and micron-size apertures in thin, free-standing films of submicron thickness. The aim of the work is to understand fundamental quantum vortex processes involved in the first onset of dissipation in superfluid flow as the velocity is increased from zero. Use is made of a high-Q superfluid resonator to excite oscillatory flow of the superfluid through the aperture and to sense the onset of dissipation. %%% This is a research effort in the area of low temperature physics. The project involves the study of superfluid helium, which does not transport heat energy as ordinary fluids. The heat energy in such systems requires generation of vortices, analogous to smoke rings, that can by generated as the superfluid moves through microscopic apertures. The research will study fundamental aspects of vortex generation and energy dissipation in superfluid helium-4. The work is of fundamental significance but may as well have technical importance in the general field of fluid hydrodynamics. The project includes computer modeling of the fluid hydrodynamics under experimental observation.