Visualization of quantum turbulence and vortex dynamics in superfluid helium

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Quantum turbulence in superfluid helium consists of a tangle of quantized vortex lines and the dynamics of these vortices provides a rich variety of physics across a broad range of length scales, particularly in the limit of zero temperature where the damping due to thermal excitations is absent. This project will utilize optical imaging apparatus that was recently developed and constructed on one of rotating dilution refrigerators to visualize quantum turbulence through the trapping of fluorescent particles (helium excimers and nanospheres) on the cores of quantized vortices. The aim is to enhance our understanding of how the dynamics of vortices contribute to the transfer of energy to shorter length scales leading to the dissipation of quantum turbulence. This will lead to an improved understanding of the general phenomena of turbulence.The student will further develop this apparatus and refine the experimental technique to improve the spatial and temporal resolution allowing a greater range of phenomena to be observed, including vortex bundles, vortex reconnections and self-reconnections, Kelvin (helical) waves, loop solitons and vortex rings. The student may also adapt the apparatus to allow imaging during steady rotation when the equilibrium state is an array of rectilinear vortex lines. Perturbing this vortex array will allow the growth and decay of inertial waves and Kelvin waves to be observed and investigated. The student will also develop software tools for analysis of the images and videos obtained from the experiment and contribute to the dissemination of the research outcomes.