Influence of Twist Pitch in CICC on Contact Condition Between Individual Superconducting Strands and a Copper Sleeve in a Lap Joint

One of the reasons for degradation of the critical current in a Cable-in-conduit conductor is unbalanced current distribution due to inhomogeneous resistance distribution in a lap joint. As a way of solving this problem, a sleeve longer than the highest order sub-cable twist pitch (cable twist pitch) and soldering a joint are actually effective to reduce the inhomogeneity in the resistance distribution between individual strands and the copper sleeve. However, the influence of individual sub-cable twist pitch on contact condition between individual strands and the copper sleeve in a CICC has not been investigated. In this study, the influence of the individual sub-cable twist pitch on contact condition between individual strands and the copper sleeve in a CICC lap joint was investigated using calculated strand paths. Our calculated results show that contact condition between strands and the copper sleeve in a CICC lap joint are improved regardless of the cable configuration when the n-th order sub-cable twist pitch is a multiple of all the previous sub-cables twist pitch. Moreover, it is shown that the difference in the characteristic associated with the contact condition and the combination of sub-cable twist pitch is caused by the cable outline.