NUCLEATION OF SINGLE VORTEX LINES IN ROTATING HE-3-B

In rotating He-3-B a large energy barrier leads to a well-defined critical rotation velocity OMEGA(c)(T,p) for the nucleation of quantized vortex lines. We have observed with cw NMR techniques the signature from single vortex lines, which nucleate at the cylindrical side wall of the rotating container proportional to OMEGA-OMEGA(c) above the nucleation threshold. Well-resolved steps are seen in the NMR absorption, when vortices enter the NMR cell and modify the order parameter texture in the presence of vortex-free counterflow. The steps have been calibrated to correspond to the nucleation of either single or multiple vortex lines, both in terms of their distance as a function of OMEGA as well as the step height.