Nucleation of vortices in superfluid3He-B
In a smooth-walled rotating container vortices nucleate spontaneously in3He-B at a critical velocityv c (T, P) which is related to the bulk superflow instability velocityv cb (T, P). This process takes place at the wall of the container. Vortices are also observed to nucleate at lower velocities in the bulk liquid in ionizing radiation. For this thermal neutrons are most practical since for them the absorption cross section is large in3He. An absorption event creates local overheating, a hot bubble in the cold superflow. An increasing number of vortex rings is observed to emerge from the bubble as a function of the superflow velocity.