STUDY ON THE EFFECT OF THE CURRENT DISTRIBUTION ON STABILITY OF A SUPERCONDUCTING MULTI-STRANDED CABLE.

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The stability of a multi-stranded superconducting cable is strongly influenced by the initial current distribution among strands and the transient current sharing after a quench of a part of stands. At first, we researched the previous studies about the stability of a multi-stranded superconducting cable. It became clear that the small deviation of the inductance of each strands for a cable in conduit conductors (CICC) may cause the large unbalance of the current distribution among strands. However, there are not enough studies which can explain the relation between the current distribution of a multi-stranded cable and its stability. We studied experimentally the characteristics of the current transfer and stability of a two-strands cable. The current transfer from the quench strand to the other strand is faster than the heat transfer between strands, when the surfaces of strands are naturally oxidized without an insulation coating. The stability of a two-strands cable becomes higher … More than that of a monolith cable because of the effect of the transient heat transfer to a liquid helium. Then a triplet superconducting cable without any coating on its surface has been used to study the influences of the current distribution within the triplet on its stability. The Minimum Quench Energies (MQE) have been measured with different initial current distributions within the triplet. It became clear that the initial current distribution, which can maximize the MQE,changes with the external magnetic fields, the total transport current and the time duration of heat inputs. The same complicated relations between the current sharing properties within the cables were obtained in the experiments of the compacted strand cable with different matrix structures and different crossover resistance. The minimum quench energies of the cable with low crossover resistance were not always larger than those of the cale with high crossover resistance. Above experimental results showed that the stability of the superconducting cable is affected with not only the current distribution properties but also other parameters such as the stability margin of a single strand, the heat transfer properties between strands and the cooling conditions. It is necessary to design the superconducing cable according to the condition of the real use of the superconducting coils. Less