The design of flat superconducting cables with considerable edge currents between the strands: coupling losses between opposite strands

The decreased contact resistance of strands close to the edges of a cable i s usually unavoidable. One has therefore to include this influence on the c oupling losses, mainly for flat structures. In addition, the concept of a c able with higher stability is a challenging opportunity to design more reli able cables using a practical approach. Namely, some additional conducting edge layer (occurring naturally or included artificially at the cable edges ) increases the amount of current, which can be transferred from one strand to another, thus increasing the stability of the cable against electromagn etic perturbations. Therefore, we calculate the total losses of such struct ures by including all contributions to the coupling losses. We show that, i n spite of the increased coupling losses, by introducing the additional wel l conducting layer close to the edges, one can compensate for the losses by producing a much higher increase in the current transfer factor between th e strands. This can lead to a more stable cable design for ac fields and cu rrents. However, it seems that the well conducting edge layer should be cut into segments whose lengths do not exceed the cabling or twist pitch. Othe rwise, the increased edge losses would be too high and detrimental to the s tability. The crucial question for cables with such segmented edge layers i s whether the increased coupling loss density close to the edges (about fou r times the maximum loss density in cables without edge sheath) is still to lerable from the cooling point of view.