Measurements on the generation and subsequent decay of vorticity in superfluid 3He-B

Recent measurements in superfluid He-3-B have been interpreted as evidence in support of the Kibble-Zurek hypothesis for the formation of defects in the early Universe. The superfluid He-3 analogue to the cosmic string is the quantum vortex. We report here the first observations on the production and decay of this vorticity in superfluid He-3-B at temperatures down to similar to 110 mu K. We detect the heat evolution of the decaying vorticity after neutron irradiation of a small superfluid He-3-B sample. We interpret the decay process in terms of a simple exponential time constant which varies inversely proportional to the quasiparticle excitation number density in the superfluid. We also observe that the fraction of the neutron energy deposited in the vorticity is consistent with the earlier measurements which supported the Kibble-Zurek hypothesis.