Quench development in thin inhomogeneous HTS film on sapphire substrate

The quench dynamics in a high-temperature superconducting thin film with a strong inhomogeneity of the critical current was experimentally studied in the circuit with a DC voltage source. The dependence of the normal zone length on time was found to be of non-monotonic character. After the normal zone propagates at some distance, it reverses the direction of its motion. The successive returns of the film sections into the superconducting state are observed. This phenomenon is explained by the dependence of thermal parameters of the sapphire substrate on temperature, in particular, a dramatic reduction of the heat conductivity of the sapphire with the increase of temperature. The numerical simulation confirms this explanation.