Near-adiabatic Quench Experiments on YBa 2 Cu 3 O 7- δ Coated Conductors

1. Near-adiabatic Quench Experiments on YBa2Cu3O7-δ Coated Conductors YBa2Cu3O7-δ coated conductors, comprised of a thin superconducting YBa2Cu3O7-δlayer deposited on a textured multilayer substrate architecture, are promising for magnet applications such as high field magnets and high efficiency energy systems. Recently, the behavior of such conductors during a sudden transition from the superconducting to normal state (“a quench”) was reported. Understanding the quench behavior is essential for building a protection system that will prevent magnet system failure. It is shown that coated conductors are difficult to quench, requiring much larger energy than Nb-based low temperature superconductors, but that once quenched, the normal zone propagates very slowly. Both the minimum quench energy and the propagation velocity are strongly depending on the sample temperature and the transport current. As the temperature increases, the specific heat of the constituent materials increases, thereby requiring more energy to disturb the conductor but also requiring larger energy dissipation to propagate the normal zone once created. Thus, the significant challenge for magnet applications will be quench detection, i.e., recognizing that a disturbance has become unstable and that localized thermal runaway is possible. X. Wang, U.P. Trociewitz and J. Schwartz,J. Appl. Phys., 101, 053904 (2007) Upper figure: Minimum quench energyas a function of transport current and operating temperature. Lower figure: Normal zone propagation velocities corresponding to the quenches in the upper figure. This work supported by the Air Force Office of Scientific Research and U.S. Department of Energy (PI: Justin Schwartz)