On the preparation of "In Situ" multifilamentary superconducting wires

The "In Situ" technique for fabricating superconducting multifilamentary composites is reviewed. The casting technique is described. Our previously reported observation of a sharp transition in the critical current density at a critical concentration is supplemented by the observation of a sharp increase in the hardness for a niobium concentration of around 15 wt %. Also observed is a sharp transition in the Jcat 12 Tesla as a function of Nb concentration again at about 15 wt %. The "In Situ" technique has now achieved overall Jc\´s comparable to those of commercial multifilamentary composites. Furthermore the mechanical properties of "In Situ" materials have improved strength. We are exploring production at larger scale by a continuous casting process.