High field scanning Hall probe imaging of high temperature superconductors

Power Applications of high temperature superconductors (HTS) are emerging rapidly towards the market place. While first generation Bi₂Sr₂Ca₂Cu₃O₁₀ (BSCCO) powder in tube (PIT) conductors are already used in the industrial sector (magnet inserts, transformers and power transmission cables), second generation Y₁Ba₂Cu₃O_7-δ (YBCO) coated conductors are being developed which promise even greater performance, particularly for applications which require high magnetic fields. Along with the development of these materials, advances in characterization techniques have enabled detailed studies of the associated loss mechanisms. In particular, magnetic imaging techniques (both scanning hall probe and magneto optics (MO)) have been able to establish the pattern of current flow within the samples, allowing study of grain boundary efficiency, current homogeneity and filament interconnection in multifilamentary PIT tapes. However, as the technology moves towards high field applications, high-field magnetic imaging is required. Presently MO is inherently limited to low fields (<0.1 T) and for this reason we have recently focused on the development of a high resolution scanning hall probe device to work in high magnetic fields. We present data showing how the current pattern evolves in the presence of high magnetic field for various samples and discuss the implications for the future development of HTS conductors.