A TUBULAR PROCESS FOR MAKING NB3SN CONDUCTORS

It has been shown that subelements of niobium or niobium alloy tubes, clad with copper and with tin or tin alloy cores can be restacked in large numbers and drawn to finished wire with few ductility problems. These multi-subelement restacks have been heat treated under a series of different conditions, the aim being to produce materials with low a.c. losses and good intermediate field stability.The process does not employ any electron beam welding, hot isostatic pressing or extrusion and, as a result, is more economical than the conventional internal-tin approach normally used for these materials.Critical current densities in the non-copper area as high as 2220 A/mm2 at 12 T have been achieved.