Big bang simulation in superfluid 3He-B - Vortex nucleation in neutron-irradiated superflow

V.M.H. Ruutu1, V.B. Eltsov1,2, A.J. Gill3,4, T.W.B. Kibble3, M. Krusius1, Yu.G. Makhlin1,6, B. Plaçais5, G.E. Volovik1,6, and Wen Xu1

1Low Temperature Laboratory, Helsinki University of Technology, Otakaari 3A, 02150 Espoo, Finland
2Kapitza Institute for Physical Problems, 117334 Moscow.
3Blackett Laboratory, Imperial College, London SW7 2BZ.
4T-6 Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545.
5Laboratoire de Physique de la Matière Condensée de l'Ecole Normale Supérieure, Unité Associée au CNRS (URA 1437), F-75231 Paris CEDEX 05.
6Landau Instute for Theoretical Physics, 117334 Moscow.

We report the observation of vortex formation upon the absorption of a thermal neutron in a rotating container of superfluid 3He-B. The nuclear reaction n + 32He = p + 31H + 0.76MeV heats a cigar shaped region of the superfluid into the normal phase. The subsequent cooling of this region back through the superfluid transition results in the nucleation of quantized vortices. Depending on the superflow velocity, sufficiently large vortex rings grow under the influence of the Magnus force and escape into the container volume where they are detected individually with NMR. The larger the superflow velocity the smaller the rings which can expand. Thus it is possible to obtain information about the morphology of the initial defect network. We suggest that the nucleation of vortices during the rapid cool-down into the superfluid phase is similar to the formation of defects during cosmological phase transitions in the early universe.

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