  The particulars of dc current passage through a structure consisting of a
doubly connected superconductor (DCS) with branches that are asymmetric with
respect to length and critical current have been investigated experimentally.
The short branch, which has the lowest critical current, was a clamping
niobium-niobium point contact with length comparable to the coherence length of
the superconductor. In contrast to a previously studied DCS with a short branch
much longer than the coherence length, it was found that when the short-branch
current reaches the critical value the currents in the branches of the DCS do
not undergo self-excited oscillations; a current exceeding the critical value
enters the long branch when this current is increased in portions (is
quantized), and when it is subsequently decreased it freezes partially or
completely in the DCS circuit.
