Optimum Filament Positions Within a MgB2 Wire Resulting in Maximum Reduction of AC Losses

Transport current capability of MgB₂ multifilamentary wires is intrinsically affected by the self and mutual magnetic inductance between superconducting filaments, which is a problem that depends on the geometrical distribution of the filaments. Any rise on this magnetic interaction can cause an increase in the AC losses of the system, which counteracts the efficiency of the wire and rises the cryogenics costs. Thus, in order to reduce the AC losses of multifilamentary MgB₂ wires by finding an optimal arrangement of the MgB₂ filaments, we present a comprehensive study for the optimal positioning of up to 7 and 13 filament wire configurations as common benchmarks. Varying the positions of the filaments within the copper matrix has shown a remarkable reduction in the AC losses of up to 60% the standard losses, a phenomenon which we have explained as a function of the calculated distributions of current density and magnetic field for the new wire designs. Likewise, a sudden rise in the AC losses of the multifilamentary wires with concentric arrangements of filaments has been found under certain configurations, where the magnetic saturation of the outer filaments can cause a notorious rise in the AC losses. This reveals how some multifilamentary designs can show enhanced energy loss characteristics whilst maintaining the same transport current conditions if a proper arrangement of the MgB₂ wires is conceived prior to its manufacturing.