Critical currents in superconductors

摘要

It is necessary to introduce structural defects which can act as pinning centers to achieve high critical current density (J_c) in type II superconductors. For example, large J_c values achieved in conventional superconducting wires were ascribed to flux pinning by alpha Ti precipitates in NbTi, and grain boundaries in Nb_3Sn. Without these pinning centers, even NbTi and Nb_3Sn wires exhibit poor J_c values.