Periodic artificial pinning centers for high critical current density of tape conductor

For high magnetic field in superconducting magnet, superconducting tape conductor with effective pinning centers is required for high critical current density. We studied periodic artificial pinning centers for use in HTS tape conductor. Periodic patterns were introduced as artificial pinning centers on a superconducting Nb film. 2 and 4 /spl mu/m period groove patterns were formed on the Nb film with various depths. Magnetization and critical current density of the films with the groove patterns were larger than those of the film without the pattern, as a result of effective artificial pinning. After regarding immanent magnetization caused by defects, films with 2 /spl mu/m period grooves had about 2 times as much magnetization as the films with 4 /spl mu/m period grooves. Ratio of pinning force density of 2 /spl mu/m period groove pattern to that of 4 /spl mu/m period groove pattern was calculated to be 2. The magnetization of both films increased with groove depth until it reached a half of film thickness. It is considered that this increase of magnetization with groove depth is mainly caused by an increase of elementary pinning force for individual flux line.