Emission of Discrete Vortex Rings by a Vibrating Grid In SuperfluidHe3−B: A Precursor to Quantum Turbulence

We report a transition in the vorticity generated by a grid moving in the $B$ phase of superfluid ${}^3\mathrm{He}$ at $T\ll T_c$. The evolution of the vorticity after arresting the grid shows a dramatic change in the decay rate at a critical grid velocity. We believe this to reflect a sharp transition from ballistic vortex-ring production at low grid velocities to quantum turbulence at higher velocities and that independent isolated vortex rings provide the precursors to the developed turbulence. Furthermore we believe that this may be a feature of all quantum turbulence arising from repetitive mechanical agitation.