Features of the thermal stabilization theory of composite superconductors: The nonlinear description of the dissipative states

Abstract

The features of the Joule's energy dissipation in a composite high-temperature superconductor with a power equation of the voltage-current characteristic cooled by liquid helium or hydrogen are discussed. It is shown that the non-standard thermal stabilization conditions of composite superconductors can exist if the nonlinear temperature dependences of the electrical resistivity of the stabilizing matrix and heat flux to liquid refrigerant are considered. First, there may be no minimum currents of the existence and propagation of a normal zone. Second, the intensive cooling of a composite superconductor by liquid refrigerant significantly increases the range of the stable currents, which leads to the existence of the supercritical applied currents. Third, an increase in the temperature of a composite superconductor may occur under the conditions close to adiabatic during irreversible propagation of the thermal instability despite its intensive cooling by liquid refrigerant. This effect must be considered when determining the burnout conditions of a composite superconductor. The performed numerical experiments are compared with the results obtained from the existing thermal stabilization theory of the composite superconductors, which is based on the linear temperature dependence of the critical current density of superconductor and jump-like transition from the superconducting state to the normal.