Contact resistance simulations and measurements of MgB2–MgB2 lap joints

Resistive joints are found in many systems using superconductors. Joints are used to connect the superconductor to a normal conducting current terminal or to connect two superconductors, for example in pancake type windings. Knowing the resistance between the contacts is important in studying the heat balance of a superconducting system. We performed several experiments with MgB2–MgB2 lap joints to determine the relation between the contact resistance and solder joint length. Also, the effect of the outer sheath material on the contact resistance was studied. To support the experiments, a computational model using Finite Element Method was created. The measured and computed results showed adequate correlation. In the experiments, the soldered joint length was varied from 3 to 20 mm resulting in contact areas between 2.5 and 16.6 mm2. The results indicated that the outer sheath material has significant effect on the contact resistance. For a Monel sheathed conductor the measured contact resistances varied between 4 and 16 μΩ and if a copper sheath was used, the resistances were an order of magnitude smaller.

► Resistance of a lap joint between two superconductors can be modeled using FEM.
► Modeling of such a joint can require reparametrization of metrics.
► Outer sheath of multifilamentary MgB2 strand has significant effect on the contact resistance.
► Simulated and measured resistances were in agreement.