Stability under transverse field pulse of the Nb3Sn ITER cable-in-conduit conductor

A section of the ITER (International Thermonuclear Experimental Reactor) conductor, left from the winding of the Central Solenoid Model Coil, was tested for stability under pulsed transverse field in the SULTAN facility, at background field up to 11 T and dc current up to 100 kA. The test was repeated at a broad range of operating temperature and for different current distribution in the strand bundle. The ability to withstand transverse field transients is compared with the predicted energy margin. For large current unbalance, the degradation of transient stability is well correlated with the decrease of quench temperature in de mode. The crucial role of the current sharing among subcables for the stability of the cable-in-conduit conductors is assessed for short samples as well as for the ITER coils. Basic recommendations are drawn for the improvement of the conductor design.