Nb[sub 3]Sn strand development at Oxford Superconducting Technology

Abstract

Oxford Instruments, Superconducting Technology (OI-ST) manufactures superconducting Nb3Sn wire via several different routes, producing conductors tailored for use in moderate to very high magnetic fields. Recently, research at OI-ST has produced internal Sn strand made by the modified jelly roll process that has achieved 12 T, 4.2 K non-Cu critical current density (Jc) values of ∼2600 A/mm2. This high Jc level was achieved by reducing the Cu content of the filament subelements, and increasing the Nb and Sn fractions. Similar high performance production strands have been used to produce the world’s highest field accelerator dipole magnet, which has reached 14.7 T. Work on bronze-processed conductor has shown that improved Jc levels can be achieved in “externally stabilized” strand relative to “internally stabilized” strand due to an improved Sn availability. OST is also involved with research for the High Energy Physics National Conductor Program. Results on internal Sn composites made entirely by hot extrusion are described. Finally, the present status of Ta-Sn powder-in-tube conductor development is presented. For such conductors, an irreversibility field ∼26 T was measured at 2.2 K.