Visualization of quantum turbulence in superfluid helium in the zero-temperature limit

The aim of the project is to observe for the first time reconnections and deformations occurring with individual vortex lines in superfluid helium at temperatures so low that there is practically no normal fluid. The project will result in images of vortex lines, their bundles and tangles in different types of turbulent flow, visualized through fluorescence of either helium excimers or dyed nanoparticles as tracers.

To achieve this, a novel technique will be developed with which one can seed vortex lines by either helium excimers or dyed nanoparticles and take images of their fluorescence, induced by a laser light. The container with superfluid helium under study will be located inside a cryostat capable of cooling below 0.1K and rotating continuously. The student will be developing the techniques of (i) making injectors of excimers and optical cells for superfluid helium, (ii) laser-induced fluorescence, (iii) imaging of very low-intensity light; he will be involved in running the cryostat, automating data acquisition and analysis, writing-up and presenting the results.

The project belongs to the EPSRC research area Quantum Fluids and Solids, but also impacts on
Fluid Dynamics and Aerodynamics. It will implement a novel method of visualization at low temperature, involving tracer particles trapped on quantized vortex lines, and will demonstrate the potential of this method for research on quantum turbulence. As quantum turbulence mimics classical turbulence on large length scales, our direct visualization of the structure and dynamics of the region of concentrated vorticity might also make an important contribution to the understanding of rare events involving vortices of large amplitude in classical turbulence.