Magneto-optical investigations as a tool to improve quality of (Pb,Bi)-2223 tapes

Flux distributions of multifilamentary (Pb,Bi)-2223 tapes are investigated by magneto-optic (MO) imaging at T=10 K and in different field orientations. This enables one to study differences between the individual filaments in a direct way. To our knowledge we have for the first time applied the field perpendicular to a cross section of an intact tape, i.e. The external field is aligned along the individual filaments. This geometry of the MO experiments enables the study of the superconducting properties of the filaments as a function of position in the tape. The flux patterns reveal the shielding properties (=critical current density) of the filaments; and the studies clearly show differences in the superconducting properties between the different filaments. Our observations provide, therefore, important information for further development of the (Pb,Bi)-2223 tapes.