Possible visualization of a superfluid vortex loop attached to an oscillating beam

TL;DR

This study visualizes a potential superfluid vortex loop attached to an oscillating beam in superfluid helium, using tracer particles and high-speed video to analyze its motion and phase relationship.

Contribution

First visualization suggesting a superfluid vortex attached to an oscillating object using tracer particles and high-speed imaging.

Findings

Observed a structure consistent with a vortex loop attached to the oscillator

The structure's motion is in phase with the beam’s velocity

Alternative models like a hydrogen filament are less consistent with observed phase

Abstract

Visualization using tracer particles is a relatively new tool available for the study of superfluid turbulence and flow, which is applied here to oscillating objects submerged in the liquid. We report observations of a structure seen in videos taken from outside a cryostat filled with superfluid helium at 2 K, which is possibly a vortex loop attached to an oscillator. The feature, which has the shape of an incomplete arch, is visualized due to the presence of solid H2 tracer particles and is attached to a beam oscillating at 38 Hz in the liquid. It has been recorded in videos taken at 240 frames per second (FPS), fast enough to take around 6 images per period. This makes it possible to follow the structure, and to see that is not rigid. It moves with respect to the oscillator, and its displacement is in phase with the velocity of the moving beam. Analyzing the motion, we come to the conclusion that we may be observing a superfluid vortex attached to the beam and decorated by the hydrogen particles. An alternative model, considering a solid hydrogen filament, has also been analyzed, but the observed phase between the movement of the beam and the filamentary structure is better explained by the superfluid vortex hypothesis.