Heat treatment optimization of internal tin Nb/sub 3/Sn strands

The development of high critical current density (J/sub c/) multifilamentary Nb/sub 3/Sn strands with low magnetization is important for many technological applications, including construction of high field accelerator magnets. To achieve this goal, strand R&D is actively pursued by Fermilab and IGC using the internal tin process. The J/sub c/ of a Nb/sub 3/Sn strand made with the internal tin technology depends on numerous factors, including Nb filament size and heat treatment cycle. Various heat treatments were applied to Nb/sub 3/Sn strands of different designs produced by IGC. The effect of filament size was studied both during the Nb/sub 3/Sn layer growth and after complete reaction. The resulting J/sub c/'s are presented, as well as SEM microscopy of strand sections.