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 theoretical ly. 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 cu rrent variation rate for both increasing and decreasing transport curr ent. The quench development process has a complicated structure with t wo stages of acceleration of the normal zone propagation rate. At curr ent derivative approximately 100 kA s-1 the appearance of several norm al spots was observed. The possible explanation for the normal zone ac celeration is the interaction between the propagating zone and thermom agnetic disturbances induced by varying current. The corresponding the ory was developed and compared with experiment.