This paper reports the discovery of a new vortex phenomenon in superfluid ${}_{}{}^3{}_{}{}^{}\mathit{B}$. A single filament of quantized vortex line precesses as a solid body around a wire extending along the axis of a cylinder. The precession frequency equals the angular velocity of the apparatus at which the presence of a single quantum of circulation minimizes the system’s free energy. The period of precession is related to the circulation quantum and the dimensions of the apparatus. Thus a measurement of the precession period is an accurate determination of the quantum unit. We find κ=(1.020±0.03)h/2${\mathit{m}}_3$, where ${\mathit{m}}_3$ is the mass of the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ atom.

• Received 8 January 1992

DOI:https://doi.org/10.1103/PhysRevLett.68.1327