FLUX-PINNING CHARACTERISTICS OF NB ARTIFICIAL PINS WITH RIBBON-SHAPE IN NB-46.5 WT-PERCENT TI SUPERCONDUCTORS

The pinning force density, F(p), of a new type of Nb artificial pin was observed in Nb-46.5 wt% Ti superconducting wires, where the artificial pins were made of thin Nb plates inserted into successive NbTi plates and were cold drawn to a ribbon-like shape. It is shown that the position of the peak of F(p) shifts systematically from the low magnetic field side to the high-field side as the reduction rate of pin thickness increases. The observed values of F(p) in the low and medium magnetic fields, such as F(p) congruent-to 19 GN m-3 at 2 T, congruent-to 22 GN m-3 at 3 T and congruent-to 20 GN m-3 at 4 T, are much larger than those in conventional NbTi wires with alpha-Ti pins, while the pinning characteristics at the high-field side show saturation-like tendency contrary to those in conventional NbTi wires. The flux pinning mechanism of the pins is also discussed.