Measurements of temperature dependence of the stability and quench propagation of a 20-cm-long RABiTS Y-Ba-Cu-O tape

Thermal stability and quench propagation in a composite tape made of YBa₂Cu₃O_x (YBCO) superconductor were studied experimentally. Quench propagation in each test was initiated by applying a sequence of a short overcurrent pulse followed by a longer pulse at a typical operating current for the tape. The resulting change in resistivity due to internal heating was measured through voltage taps across different zones of the tape. Measurements were performed as a function of both initial overcurrent and operating current for several operating temperatures between 45 and 80 K. These experimental results provided the thermal stability margin, the minimum propagation current, and the quench propagation velocity for the tape. Experimentally obtained temperature dependence of normal zone propagation velocity was compared with the adiabatic theory taking into account minimum propagation current. It was noted that the measured normal zone propagation velocity compared favorably with the theory at each operating temperature.