Influence of rapid heating condition on superconducting properties in transformed jelly-roll Nb/sub 3/Al multifilamentary wire [magnets]

Understanding the variation of the superconducting properties as a function of the maximum heat treatment temperature or heating time in jelly-roll Nb/sub 3/Al wire is important for the optimization of the rapid heating conditions. Jelly-roll Nb/sub 3/Al wires with a Nb matrix were ohmically-heated to maximum temperatures ranging from 1900 to 2300 /spl deg/C in vacuum in order to optimize the rapid heating conditions and to investigate the superconducting properties for this transformation method. The diameter of the wire was 0.94 mm. The sample was monitored using a noncontact measurement technique employing a photodiode to measure high temperatures (over 2000 /spl deg/C) during rapid heating. After the surface temperature reached a maximum, the sample was quenched in liquid gallium. The samples were annealed for 10 hours at 800 /spl deg/C after the rapid heating process to transform the bcc-phase to the A15 phase. The superconducting properties including DC magnetization and critical current were explored for various maximum heating temperatures and heating times.