Stability and normal zone propagation in YBCO CORC cables

In this work, a two layer CORC (Conductor On Round Core) cable was tested for stability and Normal Zone Propagation (NZP) at 77 K in a liquid nitrogen bath. The cable was instrumented with voltage taps and wires on each strand over the cable’s central portion (i.e. excluding the end connections of the cable with the outside world). A heater was placed in the central zone on the surface of the cable, which allowed pulses of various powers and durations to be generated. Shrinking (recovering) and expanding (not recovering) normal zones have been detected, as well as stationary zones which were in thermal equilibrium. Such Stationary Thermal Equilibrium zones (STE) did not expand or contract, and hit a constant upper temperature while the heater current persisted; they are essentially a form of Stekly stability. Overall, the cable showed a high degree of stability. Notably, it was able to carry a current of 0.45Ic cable with maximum temperature of 123 K for one minute without damage.This work was supported by the U.S. Department of Energy, Office of Science, Division of High Energy Physics, under Grant DE-SC0011721, DE-SC0007891 and DE-SC0014009.Recovering as well as non-recovering NZs have been observed in a CORC cable under quench conditions operating in liquid nitrogen and self-field. In addition, for low I/Ic cable, the existence of stationary normal zones in the cable has been seen, which are essentially a form of Stekly stability phenomenon. Several examples of propagating and non-propagating zones were explored at higher I/Ic cable fractions, and a stability diagram for the cable was generated. The CORC cable in this study showed a high degree of stability. It was able to carry a current of 45% of the cable critical current with maximum temperature of 123 K for one minute, without damage