The effect of the wire design parameters on the stability of MgB2 superconducting coils

The thermal stability of superconducting wires is one of the important issues for wire applications. We present a numerical study on the effect of the wire design parameters on the quench behavior of superconducting MgB2 wire employed in coils. The model considers a stack of MgB2 wires of rectangular cross section separated by insulation layers and subjected to a thermal disturbance. The problem is solved on a two-dimensional domain and employs the current sharing concept in the transition between superconducting and normal states. The effects of three design parameters in wire manufacturing are investigated. Quench behavior is compared for wires having different filling factor of superconducting filaments, different volume of copper stabilizer, and different residual resistivity ratio (RRR) values for copper. The results indicate that the quench propagation velocity (QPV) at 1.5 T is weakly affected by changes in the volume and electrical properties of copper, whereas the minimum quench energy (MQE) is strongly dependent on the RRR value of copper and can increase by a factor of nearly 2 with the RRR varying from 30 to 150. Both the MQE and QPV change remarkably by varying the MgB2 filling factor. The MQE drops by a factor of 6 and the QPV increases by a factor of 2 with the filling factor varying from 10.5% to 25%.