Multifilament NbTi with artificial pinning centers: The effect of alloy and pin material on the superconducting properties

Abstract

Low-temperature superconductors containing artificial pinning centers (APC) have produced record critical current densities in NbTi at magnetic fields below 4 T and promise further improvements at these and higher fields. Peak current densities are achieved when pinning center spacings are matched to spacings of the flux line lattice at the field of operation. The enhancement of Jc through inclusion of artificial pinning materials is accompanied by reduction in Tc and Hc2 through proximity effects. We find that the choice of the superconducting alloy as well as the pin material has marked effect on both the characteristic pinning force Fp and the critical magnetic field Hc2.