Effect of the dissipative states of non-ideal second-type superconductors on their current-carrying capacity

The influence of the dissipative states of non-ideal second-type superconductors on their current-carrying capacity is investigated. The study performed is based on the numerical solution of non-stationary Maxwell and Fourier equations with different features of the non-linear rise of their I-V characteristics. First, the power equation of the I-V characteristic with various n-values was used to examine the states of superconductors that occur when the I-V characteristic continuously increases. Second, the obtained results are compared with the results of computer experiments simulating the thermo-electrodynamic states of superconductors when the electric field is not present in their I-V characteristics in the subcritical current range. A piecewise linear I-V equation describes such idealized modes. The results of the simulations indicate that a superconductor's ability to carry the transport current drops as the n-value decreases. Accordingly, the maximum transport current (quench current) flowing stably through a superconductor with an idealized I-V characteristic are always higher than the corresponding value calculated for superconductor with the same critical current but with a continuously increasing I-V characteristic. Moreover, a deterioration in cooling conditions or an increase in the current charging rate will also lead to a reduction in the current-carrying capacity of non-ideal second-type superconductors. The non-trivial temperature change of superconductors during formation of stable modes should necessarily be taken into account in experiments to investigate the voltage-current characteristics of superconductors, their current-carrying capacity, and loss theory.