ANOMALOUS QUENCH PROPAGATION IN SUPERCONDUCTORS UNDER FAST CURRENT DECREASE

The normal transition of a superconducting NbTi-CuNi multifilamentary wire under fast transport current decrease (dI/dt < 0) is studied both experimentally and theoretically. The normal zone propagation velocit y v(t) is measured at \dI/dt\ up to 7.10(5) A/s. At high values of the current decay rate (\dI/dt\ > 10(5) A/s) the value of v increases sha rply and exceeds the quench propagation velocity under DC mode despite the decreasing current. To describe the observed effects theoreticall y the interaction of the propagating normal zone with the electric and thermal perturbations induced in the superconducting phase by the cha nging transport current should be taken into account. An analytical fo rmula for v(I, dI/dt) is presented which is in good agreement with the experimental data.