Simulation of the ITER Poloidal Field Coil Insert DC Performance with a New Model

The Poloidal Field (PF) Coil Insert is made from a NbTi cable in conduit conductor and has been subjected to tests in the Central Solenoid Model Coil facility at JAEA in Japan. For the interpretation of the voltage tap signals from these tests, we adapted the JackPot model – which was used previously to analyse short sample tests – to simulate also the model coil experiments. A key ingredient of JackPot is that the local magnetic field on the superconducting strands and the inter-strand contact resistances all depend on the “trajectories” of the strands within the cable. These trajectories areprecisely calculated, ensuring a realistic distribution of magnetic field- and contact resistance values. The results of the model calculations show that the applied joints are most likely responsible for the poor performance of short samples of similar PF conductors in earlier experimental tests. The model predicts that the influence of the joints is significantly less pronounced for the Poloidal Field Coil Insert

Validation of a strand-level CICC-joint coupling loss model

Calculating the coupling losses in cable-in-conduit conductor (CICC) joints requires a large amount of numerical effort, which is why the numerical system is often reduced by grouping strands together. However, to better understand the loss behaviour, and eventually the stability mechanism in such joints, a full-sized model working on the level of individual strands is more desirable. For this reason, the numerical cable model JackPot-AC has been expanded to also simulate the coupling losses in a CICC joint. This model has been verified with AC loss measurements on a mock-up joint, which was subjected to an applied harmonic field at different angles. The mock-up joint consisted of two sub-sized CICCs connected by a copper sole. For additional verification the AC loss of one of these conductors and the copper sole was also measured separately. The results of the simulation agree with the measurements, and the model therefore proves to be a useful analytical tool for examining the coupling loss in CICC joint