Experiments on the Kibble mechanism in liquid 4 He

New experiments are in progress to study the creation of quantised, vortices during a fast adiabatic passage through the lambda transition, thus modelling the production of cosmic strings, via the Kibble mechanism in the early universe. The expansion cell differs from that used in the initial experiments in several respects. In particular: it has been designed to minimise the flow of liquid parallel to surfaces which is believed to have caused some vortex creation via conventional mechanisms; and a hydraulically actuated needle-valve is used to close off the filling capillary where it enters the cell, thus isolating the sample. The results will be presented and discussed.