Results of Contact Resistance Distribution in NbTi and Nb3Sn ITER Conductor Termination

The contact resistance distribution among the current-carrying elements of three ITER conductor terminations is measured in the JORDI (joint resistance distribution) test facility at CRPP. One sample is based on Nb₃Sn strands, the other two are NbTi cable-in-conduit with different cable pattern and termination layout. The current from a 10 kA power supply is split by precision, low temperature shunt resistors into up to 96 parallel channels, each connected to the first or second cable stage of the conductor sample. The voltage drop is sensed between each current carrying element and the equi-potential surface of the joint connecting the conductor termination to the facility current leads. The current distribution in normal operation of a superconducting coil (imposed voltage) is straightforward deduced from the resistance distribution measured in JORDI under imposed current balance. For the same termination layout, the resistance distribution of the Nb₃Sn sample is much flatter than in the NbTi samples.