  Zurek suggested [Nature 317 (1985) 505] that the Kibble mechanism, through
which topological defects such as cosmic strings are believed to have been
created in the early Universe, can also result in the formation of topological
defects in liquid 4He, i.e. quantised vortices, during rapid quenches through
the superfluid transition. Preliminary experiments [Hendry et al, Nature 368
(1994) 315] seemed to support this idea in that the quenches produced the
predicted high vortex-densities. The present paper describes a new experiment
incorporating a redesigned expansion cell that minimises vortex creation
arising from conventional hydrodynamic flow. The post-quench line-densities of
vorticity produced by the new cell are no more than 10^10 m^{-2}, a value that
is at least two orders-of-magnitude less than the theoretical prediction. We
conclude that most of the vortices detected in the original experiment must
have been created through conventional flow processes.
