Precessing vortex motion and instability in a rotating column of superfluid 3He-B

TL;DR

This paper investigates the transition from laminar to turbulent vortex flow in superfluid 3He-B at low temperatures, identifying vortex instabilities and oscillations leading to turbulence using NMR techniques.

Contribution

It provides experimental evidence of vortex instability and oscillations near turbulence onset, linking vortex motion to spiral dynamics in superfluid 3He-B.

Findings

Oscillating NMR absorption signals near turbulence onset

Vortex creation rate of approximately 1 vortex per second

Association of oscillations with spiral vortex motion and vortex expansion

Abstract

The flow of quantized vortex lines in superfluid 3He-B is laminar at high temperatures, but below 0.6 Tc turbulence becomes possible, owing to the rapidly decreasing mutual friction damping. In the turbulent regime a vortex evolving in applied flow may become unstable, create new vortices, and start turbulence. We monitor this single-vortex instability with NMR techniques in a rotating cylinder. Close to the onset temperature of turbulence, an oscillating component in NMR absorption has been observed, while the instability generates new vortices at a low rate ~ 1 vortex/s, before turbulence sets in. By comparison to numerical calculations, we associate the oscillations with spiral vortex motion, when evolving vortices expand to rectilinear lines.