Quench time lag and its statistical characteristics of NbTi mechanical PCS measured with pulsed current

Abstract

This paper describes quench time lag characteristics of NbTi mechanical PCS through which pulsed current flows. The quench of the mechanical PCS takes place when the switch current is slowly increased and exceeds a critical value I/sub T0/. On the other hand, quench of the PCS through which pulsed current flows does not occur at the moment of the instantaneous current exceeding I/sub T0/, but takes place after a time delay T/sub D/. The quench time lag T/sub D/ depends on rise time and peak value of the pulsed current I/sub p/. A theoretical model is proposed to show that T/sub D/ corresponds to time in which a superconducting connection bridge is heated up to a critical temperature mainly by flux flow loss. T/sub D/ sharply fluctuates when I/sub p/ is just over the static critical current I/sub T0/, but remarkably decreases when I/sub p/ is further increased. It is found that statistical characteristics of T/sub D/ are well fitted to the Weibull distribution function.