Numerical simulation of thermal stability of a small coil using a Ta-barrier MgB ₂ multifilamentary superconducting wire

We have fabricated a small test coil with an A1N former by employing Cu-Ni sheathed Ta barrier MgB ₂ multifilamentary superconducting wire. An overcurrent was applied to the coil conduction-cooled in an initial temperature range between 10 K and 30 K to investigate its thermal stability by measuring temperature distribution in the winding and the terminal voltage after the application of overcurrent.We have also developed numerical model and numerically calculated the responses of the test coil to the overcurrent by simulating the electrical and thermal process with a finite element method and V-l characteristics of the coil. The comparisons of the numerical results with the experimental results show that the terminal voltage and the temperature distribution are rather well reproduced by the numerical model. The temperature dependence of thermal runaway current and total heat generation for the thermal runaway are also discussed in relation to the overcurrent by the numerical model.