Fabrication and superconducting properties of multifilamentaryMgB2 conductors for AC purposes: twisted tapes and wires with very thin filaments

Abstract

In order to use MgB2 conductors for AC applications, research and development efforts have to be carried out ontheir architecture and sheath material to minimize the AC losses. This paper will presentthe fabrication and characterization of two types of ex situ powder-in-tube processed pureMgB2 conductors with properties making them good candidates for AC industrialapplications: a multifilamentary tape with 12 filaments with a twisting pitch down to17 mm and a 361-filament wire with an average single-filament size of about 30µm. Concerning the twisted tapes we will present values of critical current density of about105 A cm−2 at 4.2 K and 2 T and we will show that it is possible to achieve a proper compromise betweenthe tape size, the twisting pitch length and the critical current density to face a reduction ofthe critical current density as a consequence of the strain on the filaments. Concerning the361-multifilamentary wire we will show appreciable values of critical current density of about5 × 104 A cm−2 at 4.2 K and 2.5 T which, together with the advantages given by the high number of verythin filaments and the non-magnetic matrix, could justify their employment.