Title : Quantum vortices in helium II decorated with solid dihydrogen particles
Contact : Nathanael Machicoane
Abstract : Quantum vortices in helium II are the building block of all superfluid flows. At the Institut Néel, we have developed the only cryostat in the world today capable of decorating vortices with micron-sized particles of solid dihydrogen under controlled and reproducible experimental conditions. This device allows us to study these quantum objects by direct visualization. Using 3 fast cameras and a sensitive high-resolution camera, we are able to reconstruct the trajectories of the dihydrogen flakes trapped on the core of the vortices. Furthermore, the cryostat and instrumentation are mounted on a rotating table, which allows the generation and study of vortex arrays aligned with the rotation axis. This canonical state (analogous to the Abrikosov lattice in superconductivity) is used as the basic configuration in all flows we consider. In this presentation, we will briefly describe the setup and present the first results : study of the regular lattice as a function of the rotation rate (verification of Feynman’s rule), study of the waves propagating along vortices forced by a thermal counter-flow, and visualization of vortex/vortex reconnections.