Quantised vortex line visualisation in superfluid helium using low-temperature optics

An optical probe based on the technique of shadowgraphy is proposed that would enable visualisation of the surface depressions (dimples) above quantised vortex lines in a sample of rotating superfluid liquid helium. An analysis based on the dimple profile calculated by Sonin and Manninen shows that the technique is feasible from the known sensitivity of our shadowgraphy system used to visualise thermal convection rolls. Such a probe could be used to investigate vortex arrays in the presence of appreciable normal component, would provide information on the profile of the dimples, and could be adapted to visualise quantum turbulence. (C) 2003 Elsevier Science B.V. All,rights reserved.