Multifilamentary Nb3Sn conductor for fusion research magnets

In an attempt to meet the eventual needs of fusion magnets, a multifilamentary Nb3Sn conductor has been proposed consisting of a cabled array of multifilamentary Nb3Sn strands .027 cm in diameter, surrounding a stainless steel core. This cable assembly would be jacketed with soft copper to provide an overall rectangular exterior. For the purpose of testing this concept, a prototype cable was fabricated in a length of several hundred meters. The cable was designed to carry 300 amperes at 12T and have a minimum bending radius of about 6 cm. Fabrication techniques, short sample critical currents and bending test results will be presented, and the problems anticipated in scale up will be discussed.