Joule heat release in a superconducting composite under a transport current charge

Abstract

The physical peculiarities of temperature dependence of heat release in a composite superconductor induced by varying transport current are analysed. The proposed investigation was based on a model describing the simultaneous thermal and electromagnetic processes inside the composite superconductor with nonlinear current–voltage characteristic correctly. Numerical solutions of the set of Fourier and Maxwell's equations were used. The analytical expression of the heat release in the superconducting composite during the flux-creep regime is found for its stable superconducting state. The results are compared with the well-known formulae describing a current-sharing approximation of heat generation in the superconducting composite. It is shown that for a high rate of current charging and with a low heat transfer coefficient, the Joule heat generation in a composite increases both in the stage of the steady superconducting state and during the development of instabilities. In particular, the value of generated heat release may differ by several orders of magnitude from the amount of heat induced by slower rates of a current charge. In these cases a notable increase of the superconductor temperature is observed during the entire process of current penetration. Therefore, for a high rate of current charge and with low heat transfer coefficients, the value of the heat released in a superconducting composite is notably larger, through the entire charging process, than would be calculated from the existing thermal stability theory.