The Effect of an Axial Moment on Normal-Phase Propagation in Type II Superconductors Carrying a Current

Abstract

A heat pulse of suitable magnitude applied locally to a wire of a type II superconductor carrying a steady transport current will initiate a small normal region. This normal region will propagate along the conductor if the rate of generation of Joule heat ρJ² is greater than the rate of heat flow to the outside and the neighboring region. The problem of the one-dimensional thermal propagation of this normal front has been studied by a number of workers.^1,2 The propagation is due to the flow of heat from the normal volume, where heat is produced at a constant rate ρJ², into the cooler superconducting region. The traveling superconducting—normal interface is taken to be at the critical temperature T _c (H) characteristic of the applied field H. Measurements on bare wires of Nb—Zr alloys as a function of current and magnetic field’ showed that the velocity of propagation was approximately linear in the current density J and independent of the normal-state resistivity ρ _n. The slope of velocity vs. J was found to depend mainly on the thermal capacity and the transition temperature T _c (H) (hence on the magnetic field).

The research for this paper was supported (in part) by the Defence Research Board of Canada Grant Number 5410-10.