Behavior of Cable Assembled With Conduit for ITER Central Solenoid

We describe herein the characteristics of a Nb₃Sn cable inserted into a conduit (cable-in-conduit conductor) for the International Thermonuclear Experimental Reactor toroidal field (TF) coil and central solenoid (CS). During insertion, the pulling force almost linearly increases as a function of the length Ii of cable is inserted. The slope of these curves for the CS cables are approximately 74% that for the TF cable, although the mass per unit length of the CS cable is approximately 63% that of the TF cable. Thus, friction between the CS cable and the conduit is slightly greater than that between the TF cable and the conduit. The number Np of rotations at the cable point for the TF cable increases to 50 almost linearly versus Ii. For I_i <; 150 m, Np for the CS cables also increases almost linearly with a slightly greater slope than for the TF cable. However, the slope decreases, and Np becomes constant at 30 for Ii ) 600 m. During compaction, the number Nt of rotations at the tail of the TF cable, the 613-m-long CS cable, and the 918-m-long CS cable increases almost linearly versus compacted cable length to 23, 36, and 69, respectively. The X-ray transmission imaging of the CS conductor clarifies the distributions of the fifth-stage twist pitch of the cable (Ip) over the entire length of the conductor. These results are consistent with a geometric analysis based on Np and Nt. The results for Ip peak at the cable point; thus, a sample of the conductor should be taken from the point to investigate how Ip elongation affects conductor performance.