ACCELERATION OF NORMAL ZONE PROPAGATION IN SUPERCONDUCTORS WITH CHANGING CURRENT

The normal zone propagation in superconducting multifilamentary wires with changing currents was studied both experimentally and theoretically. The quench in a wire was induced by a fast increase in current. It was found that the normal zone propagation velocity depends on the current variation rate for both increasing and decreasing transport current. The quench development process has a complicated structure with two stages of acceleration of the normal zone propagation rate. At current derivative approximately 100 kA s-1 the appearance of several normal spots was observed. The possible explanation for the normal zone acceleration is the interaction between the propagating zone and thermomagnetic disturbances induced by varying current. The corresponding theory was developed and compared with experiment.