Transport ac losses and screening properties of Bi-2223 multifilamentary tapes covered with magnetic materials

DC current-voltage characteristics and transport ac losses in Bi-2223 multifilamentary tapes covered with different magnetic materials were measured. The results are compared with those without the magnetic cover. Also the measurements of screening properties of the magnetically covered tape exposed to a magnetic field generated by another parallel Bi-2223 tape with different orientations of the current were performed. The iron powder was found to be an effective magnetic screen to decouple the tapes. Transport ac losses of the magnetically screened tape were not affected by the current in the neighbouring tape. It was found that the presence of a continuous magnetic cover decreases the critical current I-c of Bi-2223 tape by about 20%. In the range of currents 0.5I(c) - I-c, the total losses in the Bi-2223 tape covered with iron powder were increased 2.5 times, including the losses in the iron. (C) 2000 Elsevier Science B.V. All rights reserved.