  A convenient method to create vortices in meta-stable vortex-free superflow
of 3He-B is to irradiate with thermal neutrons. The vortices are then formed in
a rapid non-equilibrium process with very distinctive characteristics. Two
models were suggested to explain the phenomenon. One is based on the
Kibble-Zurek mechanism of defect formation in a quench-cooled second order
phase transition. The second model builds on the instability of the moving
front between superfluid and normal 3He, which is created by the heating from
the neutron absorption event. The most detailed measurements with single-vortex
resolution have been performed at temperatures close to Tc. We present an
overview of the main experimental features and demonstrate that the
measurements are consistent with the Kibble-Zurek picture. New data, collected
at low temperatures, support this conclusion, but display superfluid turbulence
as a new phenomenon. Below 0.6 Tc the damping of vortex motion from the normal
component is reduced sufficiently so that turbulent vortex dynamics become
possible. Here a single absorbed neutron may transfer the sample from the
meta-stable vortex-free to the equilibrium vortex state. We find that the
probability for a neutron to initiate such a turbulent transition grows with
increasing superflow velocity and decreasing temperature.
