A dynamic model for flux jumps in type-II superconductors

The behavior of flux jumps in hard type−II superconductors can in principle be described by solutions of coupled thermal and magnetic diffusion equations. A simple magnetic diffusion equation for hard type−II superconductors based on the flux−flow concept is proposed and numerical solutions are presented for physical parameters corresponding to a sample of NbTi. Although simplifying assumptions, such as adiabatic conditions and the Jc independence of magnetic field, are made, both the threshold field of stability and the rate of flux collapse are found to agree at least qualitatively with epxerimental values obtained in a NbTi rod. Calculated sequences of magnetic field, temperature, and power density profiles occurring during flux jumps are presented.