UC Davis

We present measurements of how a single vortex line in superfluid helium interacts with a macroscopic bump on the chamber wall. Rather than observing a unique pin location, we find that a given applied velocity field can support pinning at multiple sites along the bump, both near its apex and near its edge. We also find that a vortex can pass near or even traverse the bump itself with or without pinning, depending on its path of approach to the bump. We discuss our results in light of past computational work on vortex pinning by a hemispherical bump, as well as our own simulations that incorporate additional aspects of the experimental setup. © 2014 American Physical Society.