Superconducting properties and rapid heating condition in transformed jelly-roll Nb3Al multifilamentary wires as a function of maximum ohmic-heating temperature

Jelly-roll Nb3Al wires with a Nh matrix were ohmically-heated to maximum te mperatures ranging from 1800 to 2300 degreesC in vacuum in order to optimiz e the ohmic-heating conditions and to investigate the superconducting prope rties for this transformation method. The diameters of these wires were 0.8 0-1.34 mm, Surface temperature at the central point of the sample was measu red by a photodiode during rapid ohmic-heating. After the surface temperatu re reached a maximum, the sample was quenched in liquid gallium, All the sa mples were annealed at 800 degreesC for 3-25 hours after the rapid heating process to transform the bcc-phase to the A15 phase. Critical currents were measured up to 23 T, The samples heated to 2000 degreesC showed a maximum critical current density of 64 A/mm(2) at 20 T, The critical current densit y decreased with increasing maximum temperature during rapid heating, This paper describes the superconducting properties, the rapid heating condition s and the achievement of high critical current density at high magnetic fie lds.