Numerical analysis of the DC performance of ITER TF samples with different cablingpattern based on resistance measurements on terminations

Abstract

The DC transport properties of ITER TF conductors are analyzed inthe SULTAN facility, but their associated current sharing temperature(Tcs) can give scope for different interpretations. To extract the conductor’s pureperformance during such short sample tests requires a detailed quantitative modelsuch as JackPot, for which as many as possible input parameters are based onexperimentally verified data. The crucial interstrand contact resistance data of theTFPRO-2 and TFJA-3 samples, which have a different cabling and joint layout,has recently become available. With only three parameters for JackPot’s jointmodel, we were able to find a good match between the measured and simulatedinterstrand resistances for all terminations, despite their different layout. ForNb3Sn conductors, the axial strain is the only free model parameter left for matching the simulations withSULTAN Tcs tests. We were able to find a match with the measured voltage–temperature characteristicfor all but one conductor. The simulation results indicate that the termination layout canbe the cause of lower sample performance due to current imbalance. The outcome of thisanalysis also confirms that transverse load degradation can be significantly mitigated byfinding an optimal set of cable twist pitches.