Review of Current Distribution Measurements and Reconstruction in Cable-in-Conduit Conductors for ITER

The cable-in-conduit conductors (CICC) for ITER magnets consist of more than thousand superconducting strands. Usually such cables exhibit a significant non-uniform current distribution between the strands due to inequality of strand impedances. This undesirable effect can complicate the measurement of the conductor critical transport properties, particularly for short samples. To improve the interpretation of measurement results, detailed knowledge of the current distribution is highly desired. We present a review of current unbalance measurements and current distribution reconstruction techniques in CICC as they were intensively performed during the last years. The experimental methods of current unbalance detection are described, starting with earlier attempts on sub-size CICCs and ending with more sophisticated methods on full-size conductors. The models of current identification developed by various research groups are briefly compared, emphasizing their similarities, differences and limitations. Finally, the results of current unbalance reconstructions performed by different groups on several full-size CICCs are discussed together with the implication of the results for ITER short sample conductor tests and coil performance.