  We consider scattering of a three-dimensional particle on a finite family of
delta potentials. For some parameter values the scattering wavenctions exhibit
nodal lines in the form of closed loops, which may touch but do not entangle.
The corresponding probability current forms vortical singularities around these
lines; if the scattered particle is charged, this gives rise to magnetic flux
loops. The conclusions extend to scattering on hard obstacles or smooth
potentials.
