Effect of cyclic loading and conductor layout on contact resistance of full-size ITER PFCI conductors

An evolution of the contact resistances (R_c) of two full-size ITER (International Thermonuclear Experimental Reactor) cable-in-conduit conductors (CICC) aimed for the Poloidal Field Conductor Insert (PFCI) was studied in the Twente Cryogenic Press. The conductors are distinguished by the presence of stainless steel wraps around the last stage sub-cables in one of the conductors. The R_c and AC loss were measured on the conductors being in the "virgin" state and after they have been loaded 40,000 times with a peak force of 315 kN/m. The test results are compared with those, obtained on sections from the same conductor lengths, in the SULTAN test facility. The consequences of the cyclic loading and the sub-cable wraps on the R_c and the coupling AC loss are discussed in view of the previously published results on full- and sub-size ITER NbTi CICCs. Special emphasis was paid to the measurements of the contact resistances between individual sub-cables and the conduit, since the knowledge of them is important for proper interpretation of the DC test results. As a final goal, the test outcome will be used as a reference for calibration of the PFCI AC loss performance.