Transient performance of a prereacted epoxy-impregnated Nb3Sn racetrack coil

The superconductor coil is made up of an eight-strand rectangular cable with dimensions of 1.09*2.21 mm. The strands measured 0.57 mm in diameter before cabling, and each contains 19 subelements of 1182 filaments each. The mean filament diameter prior to reaction was 1.2>or approximately=, and the radius to the outermost filaments is 0.20 mm. A diffusion barrier separates the copper stabilizer from the subelement region. The volume fractions are 0.05, and 0.48, and 0.47 for the barrier, stabilizer, and subelement region, respectively. The coil was tested at ramp voltages from 1 to 104 V, corresponding to field ramp rates of 0.05 to 5 T/s. The test yielded a very high current density at low ramp rate and a falloff of the coil current with increasing ramp rate. The conductor, coil design and fabrication, and observed performance are described.