Cable Behavior During Manufacture of a 900-m Scale CICC

The International Thermonuclear Experimental Reactor (ITER) magnet system is composed of four kinds of large superconducting magnets. Those magnets are manufactured by using cable-in-conduit conductors (CICCs). In the production process of the CICCs, the superconducting cable is inserted into a stainless steel jacket. In a previous study, the rotation of the cable was observed during the insertion. Moreover, the twist pitch of the cable was elongated by the rotation. The influence of the fifth stage twist pitch on the conductor performance is smaller than the lower stage twist pitch. However, longer twist pitches could restrict good current transfer in the joint region in the production of ITER coils. It was difficult to observe the behavior of the twist pitch elongation in the whole length of the cable, because the cable was covered by the jacket. In this study, the dummy cable was inserted into the jacket with windows to investigate the fifth stage twist pitch, rotation, and torsion of the cable in whole length. After insertion, it was found that the cable was untwisted and twisted at the point and tail of the cable, respectively. Moreover, the distribution of the twist pitch can be estimated from the rotation of the cable at the point and the entrance of the jacket during the insertion of the dummy cable. The fifth stage twist pitch distribution can be evaluated from both rotations in the production of the central solenoid conductors.