PENETRATION DYNAMICS OF A MAGNETIC-FIELD PULSE INTO HIGH-T-C SUPERCONDUCTORS

The penetration of a magnetic field pulse into a high-T-c superconduct ing plate is investigated experimentally and theoretically, it follows from our experiments that the threshold of penetration increases with increasing amplitude and/or decreasing duration of the applied pulse. The penetrating field continues to grow as the applied magnetic field decreases. The peculiarities observed are explained in the framework of the extended critical state model. It appears that the deviations f rom Bean's classical critical state model are characterized by a param eter equal to the square of the ratio of plate thickness to skin depth . The applicability of the classical critical state model is restricte d by the condition that this parameter is much less than 1. This condi tion is also the criterion for the applicability of pulse methods of c ritical current measurements.