Peculiarities of dissipative phenomena in coated YBCO tapes carrying constant current during flux creep

Abstract

The effect of the flux creep on the dissipation phenomena in tapes based on YBCO leading to the essentially non-linear voltage-current characteristic of a superconductor is discussed. The obtained results are compared to the calculations made in the framework of the existing thermal stabilization theory based on the model assuming a jump transition from a superconducting state to a normal one. It is shown that the latter model incorrectly describes the dissipation modes, first of all, in a temperature range up to the critical temperature of the superconductor. It is proved that the type of nonlinearity of voltage-current characteristics has a significant effect on the dissipative phenomena in tapes in this temperature region. As a result, the allowable currents stably flowing in superconducting tapes may be higher than a priory defined critical current determined for continuously rising voltage-current characteristic. Correspondingly, the critical current of high-Tc superconducting tapes, which is determined using continuously increasing voltage-current characteristic, has no physical meaning. Therefore, fundamentals of the thermal stabilization theory must consider the real temperature dependence of the dissipated energy in high-Tc superconducting tapes, which depends on the nonlinearity of their voltage-current characteristic.