Investigation of the propagation velocity of a normal-conducting zone in technical superconductors

Abstract

In technical superconductors, the transition from the superconducting to normal conducting state is accompanied by a flux change outside the conductor. This is due to a difference in the current distributions between the superconducting and normal conducting states. This effect was used to apply pick up coils as sensors for detecting the transition zone and to establish a method for measuring the propagation time. The quench propagation velocities were measured, in most cases, up to the critical field and current values of the conductors. The highest measured velocity at this critical point for the low field region at 1T was about 80 ms −1 and it decreased with increasing magnetic field. The quench propagation in a superconductor additionally stabilized by soldering to one side a high purity aluminium tape was only significantly reduced by the aluminium up to 0.61 c.