Propagation of a normal zone along superconducting wires suspended in a liquid helium bath

Experimental and theoretical normal zone velocities have been obtained for superconducting tin wires in a normal and superfluid helium bath. Published theoretical calculations assume a flat normal-superconductor (N-S) boundary. A shape of the N-S boundary that results from a radial destruction of superconductivity in the moving front is calculated. For the sample in superfluid helium, the calculations are in good agreement with the experimental data. In normal helium no agreement between experimental and theoretical data can be obtained without introducing a transient heat transfer coefficient between the wire and the bath.